Theros- hunter and scout

Theros

Theros:  Either Hunter or Beast Master Ranger will be applicable. Animal companions will be invertebrates such as giant ants, wasps, ankhegs, etc.

Tocsin

Tocsin

Tocsin: The college of valor is a good choice for a Tocsin.  Remember that their role is to moderate communication through the colony as well as inspire during battle or work. Their instruments are commonly flutes and horns used to alarm and inspire nest mates.  These instruments are built robustly so that they can double as drum sticks to send signals deep within the tunnel warren through vibrations in the walls.

Terrarch healer and warren builder

Terrarch

 

Terrarchs: Because they live underground, it should be no surprise that their clerics are focused on the Earth Domain.

There may be a better homebrew earth domain cleric out there, but try this:

Earth Domain Spells

Cleric Level                  Spells

      1st             Meld into Stone, Earth Tremor

      3rd            Erupting Earth, Stone Skin

      5th            Wall of Stone, Transmute Rock

      7th            Move Earth, Flesh to Stone

      9th            Disintegrate, Earthquake

Bonus Cantrip

At 1st level you automatically gain the Magic Stone and Mold Earth cantrips. 

Channel Divinity: Summon Earth Elemental

At 2nd level you may use your channel divinity to Conjure minor Elementals (earth) of a combines CR of 1/4 your level. Thus at 8th level you could conjure one earth elemental CR 2 or two CR 1, or four CR 1/2, etc.

Channel Divinity: Summon from the Plane of Earth

At 6th level when you use your Channel Divinity  to conjure minor earth elementals, you have a 10% chance of summoning a Galeb Duhr. This chance increases by 1% per level above 6th.

Crystal Carapace

At 8th level you grow a permanent crystaline layer to your flesh that provides advantage against non-magical Slashing (not bludgeoning or Piercing) damage.

Earth Walk

At 17th Level you may move through earth at your walking speed.

                            

Swarm Lord- Master of vermin hordes

Swarm Lords

Swarm Lord: The Swarm Lord can be built fairly easily from a druid of the circle of the moon with the following changes:

 Circle of the Swarm

 As Circle of the Moon, with the following changes:

At 2nd level All Circle Forms you take must be invertebrates (Ex. Ants, wasps, crabs, centipedes, worms, octopus, etc.).

At 6th level and beyond, forms like Thri-Kreen, Ankhegs and Umber Hulks of appropriate CR level may be taken.

In place of Elemental Wild Shape-

Swarm: At 10th level you can expend two uses of Wild Shape to take on the form of an Insect Swarm of a chosen type.

In place of Thousand Forms-
Swarm Lord: At 14th level you gain Insect Plague as always prepared and it does not count against the number of prepared spells for the day.  When in Swarm form, you may take control of the Insect Plague, add its damage to your own form and eliminate the concentration requirement.

Termidon- the defender of terman warrens

Termidon

The one class which is not easily adapted by tweeking another class is the Termidon or Termen Defender.  This is a build off of the Eldritch knight.

Termidons combine the martial mastery of fighters with an alchemical ability to alter their own bodies to produce spell-like effects. This limits their spell choice to those that focus on acid, poison, or alterations of their internal chemistry.

Spellcasting:

 When you reach 3rd level, you gain the ability to cast spells.

Cantrips. You learn two cantrips from the eldritch knight spell list. You learn additional Termidon cantrip at 9th level, and a fourth at 15th level.

Spell Slots. The Termidon Spellcasting table shows how many spell slots you have to cast your spells of 1st level and higher. To cast one of these spells, you must expend a slot of the spell’s level or higher. You regain all expended spell slots when you finish a long rest.  For example, if you know the 1st-level spell chromatic orb (acid or poison) and have a 1st-level and a 2nd-level spell slot available, you can cast chromatic orb using either slot.

Spells Known of 1st-Level and Higher. You know two 1st-level spells of your choice from the Termidon spell list.  The Spells Known column of the Termidon Spellcasting table shows when you learn more Termidon spells of your choice. Each of these spells must be of a level for which you have spell slots. For instance, when you reach 6th level in this class, you can learn one new spell of 1st or 2nd level.

 .. Additionally, when you gain a level in this class, you can choose one of the Termidon spells you know and replace it with another spell from the Termidon spell list, which also must be of a level for which you have spell slots.

Spellcasting Ability. Constitution is your spellcasting ability for your Termidon spells, since you learn your spells through alterations to your own body through alchemy. You use your Constitution whenever a spell refers to your spellcasting ability. In addition, you use your Constitution modifier when setting the saving throw DC for an Termidon spell you cast and when making an attack roll with one.

 Spell save DC = 8 + your proficiency bonus + your Constitution modifier
 Spell attack modifier = 10 + your proficiency bonus + your Constitution modifier

Frontal Gland. At 3rd level, you develop a glandular pore in your forehead.  This will be the focus of the alchemical alterations of your body to produce spell effects.  Your spells do not require components and may be cast as long as this structure is undamaged.

War Alchemy. At 7th level, when you use your action to cast a cantrip, you may make one weapon attack as a bonus action.

Pack Tactics. At 10th level, you have advantage against a target if at least one of your allies is within  5 feet and is not incapacitated.

Vulnerable Strike. At 15th level, your strike damages a creature in a way that makes it vulnerable to acid or poison.  When you hit a creature, that creature has disadvantage on the next saving throw it makes against a spell you cast that causes acid or poison damage before the end of your next turn.

Improved War Alchemy. At 18th level, when you use your action to cast a spell, you may make one weapon attack as a bonus action.

Termidon Spellcasting
Fighter      Cantrips       Spells      —Spell Slots per Spell Level—
Level         Known         Known          1st 2nd 3rd  4th  5th
     
3rd               2                   3                 2   —   —   —   —
4th               2                   4                 3   —   —   —   —
5th               2                   4                 3   —   —   —   —
6th               2                   4                 3   —   —   —   —
7th               2                   5                 4   2    —   —   —
8th               2                   6                 4   2     1    —   —
9th               2                   6                 4   2     2    —   —
10th             3                   7                 4   3     3    —   —
11th             3                   8                 4   3     3    —   —
12th             3                   8                 4   3     3    —   —
13th             3                   9                 4   3     3     2    —
14th             3                 10                 4   3     3     2    —
15th             3                 10                 4   3     3     2    —
16th             3                 11                 4   3     3     3    —
17th             3                 11                 4   3     3     3    —
18th             3                 11                 4   3     3     3    —
19th             3                 12                 4   3     3     3     1
20th             3                 13                 4   3     3     3     1

Termidon Spell list

Some spells are limited to Acid or Poison damage.  Some spells require a shift to Acid damage from another type to reflect a different mode of action.  For example as switch to acid damage turns Aganazzar's Scorcher into a stream of acid like Black Dragon breath.  Many spells can only be cast upon your self to reflect the ability to use alchemy to heal or resist damage.

Cantrips
       Acid Splash
       Poison Spray

Level 1
       Chromatic Orb (Acid or Poison)
       Cure Wounds (self)
       Ensnaring Strike (Sticky glob causing Acid not piercing damage)
       False Life

       Fog Cloud
       Goodberry
       Grease
       Hellish Rebuke (Range touch, acid damage)
       Heroism (self)
       Absorb Elements (Acid or Poison)

       Ray of sickness

Level 2
       Anagazzar’s Scorcher (stream of Acid not fire damage)
       Alter Self
       Barkskin (Chitin)
       Blindness
       Darkvision (self)
       Enhance Ability (self)
       Enlarge/Reduce (self)
       Lesser restoration (self)
       Protection from Poison (self)
       Web

Level 3
       Elemental Weapon (Acid)
       Feign Death
       Haste (self only)
       Protection from Energy (Acid or Poison)

 Level 4
       Vitriolic Sphere
       Death Ward
       Elemental bane (acid)
       Freedom of movement

 Level 5
       Contagion
       Greater Restoration
       Cloudkill
       Regenerate

Not your Daddy's Dromites. By Paul Michael Bardunias

The termen looked too, well, elfy to make good weapon smiths, but Gunner vouched for them. He was our Master Smith, so we went where he sent us.  When good, squared, dwarven work gave way to rounded, flowing, tubes that looked as if eroded by an underground river, I knew we had reached the terman warren.  The chittering crowd that greeted us was a motley mix of sizes.  The little ones were the most common. No bigger than a gnome, and if anything more spindly, with those four arms waving about.  They took the tools and ingots we brought and loaded them on those giant termites they ride.

We left our gear and passed through a cordon of their warriors, tall as a good sized dwarf, but slim behind their big shields and lances that looked to awkward for a tunnel like this. They smelled like wine gone to vinegar.  We were received by one of their princes.  You could mistake him for an elf in a dark tunnel.  He carried himself like he was used to being obeyed, and with all four of his hands on the hilts of dwarf-made weapons, I was not about to comment on his elfyness.  He was flanked by some sort of holy man and another with a flute and drum. He greeted us formally, then bade us move quickly, for we were just beneath an elven outpost and there had been clashes recently.  As if in explanation, he cocked his head whimsically, and showed us a shard of dark wood with elven script inscribed before popping it in his mouth.

I could tell we were walking up a slight incline for about a mile when the whole column suddenly halted.  A phalanx of those guys with the big shields moved to block the tunnel ahead where a band of elves had broken in.  We watched as the elvish bowmen became a blur behind the tide of arrows that washed down the tunnel.  The big shields of the termen sprouted elven arrow shafts like the quills of a hedgehog. When the barrage of arrows proved ineffective, those prissy little elf swordsmen attacked.  The long lances of the termen suddenly made sense, for not a single elf could come to grips with a terman in line.  When the elf swordsmen pulled back, I knew what was coming.  Sure enough, a brace of elven mages sprouted fire between upraised hands in a blinding flare of light.

A sudden blast of sound echoed through the tunnels from the flute player behind us, a shrill note that made me instinctively cover my ears.  Darkness descended once more as the fires died when the mages recoiled from the noise lost concentration on their spells.  Just then, that holy man chanted in his chirping voice and a wall of earth grew from the tunnel floor.  Not in front of the elves as you might expect, but behind them.  Trapped elves! It does a dwarven heart good.  I looked at my mates and our hammers came out.  But as we moved forward, on of those little termen ahead restrained us and said we must halt and watch.  Just as I had decided on showing this little runt what happens to anything coming between a dwarf and an elf in need of thumping, an acrid smell almost floored me.

One after another, those big warriors spouted off.  Gouts of acid shot from their heads like so many little black dragons, and the elves clawed at the wall of earth as the flesh sizzled off of their bones.  I was suddenly very happy to be arming these people. This was the use that dwarven steel was forged for.  I almost felt bad for the thrice-damned elves…almost…
           

                                                                        -Thorbald Thunderfoot, My Time Among The Termen.

Termen ate their way to sentience.  They sprung from humble termites that consumed the mage-wrought wooden palaces of the elves.  Their form evolved over time, with bodies becoming a blend of insect and elf.  Although the magic of the elves spurred their evolution, to elves they are little more than vermin.  It was the dwarves that first brought knowledge of other civilizations to the termen and taught them the art of metal smithing.  In many lands the tunnels of dwarves and termen intersect, leading to agreements on mutual defense.

Termen have four arms and two legs, large opaline eyes, and prominent antennae. They have faces that are generally hard to read by other races, because they convey a wide variety of emotions with simple tilts, nods or bobs of the head and the inclination of antennae.  Their flesh ranges from cream to light green in color, with a reddish hue to areas where the cuticle is thicker like the head, chest, and forearms.  In the warm humidity of their home tunnels they were minimal clothing, but may be found heavily swathed in flowing robes when moving through the outer world.

Everywhere and nowhere

Warrens of tunnels extend through the soil of many lands, but few will have seen them.  Colonies can be found in deep forests within the boles of huge trees or rising high above the savanna in towers of clay.

Insular and Secretive

Termen are fanatically loyal to their colony mates.  This may at times be transferred to groups they join outside the colony.  Conflict may arise when they expect such loyalty to be returned. Colonies usually engage in constant border skirmishes, but whole colonies will at times march to war.  These massive armies can take over other colonies or destroy whole cities of humanoids. They get along well with dwarves and gnomes. Elves and evil humanoids are hated foes.  Of course treants are not fond of termen!

Adventuring Termen

Termen are usually loathe to leave their colony.  Most will never see the light of day.  Exceptional individuals, usually males, but sometimes females are pushed to leave the colony in order to establish a heroic reputation and learn the skills to challenge for the right to become Royal caste and lead a colony.

Cultural Details

Alignment. Termen tend to be neutral, the concepts of good and evil are something they often find difficult to reconcile with their first moral imperative: Do what benefits the colony. They are usually lawful because they have been reared in the strict discipline of the colony. Individuals may vary, especially when away from the structure of the colony.
Religion. Each large colony forms its own deity.  A terman worships the spirit of his home community as a goddess, with the queen its high priestess.  The one deity all termen worship is Termes the Swarm King, who represents the whole species and is shared by all colonies.

Terman Names
 Both male and female termen have names composed of three parts: a personal name, the name of their birth colony and a caste name.
Personal name: Zza, Kreel, Djm, Maa

Colony names: Khopt,!zil, Ka’chri, Zrikriri, Xsifu

Caste name: Kra’en, Barz, Ghuum, Mbun, Tiz

Example: Zza Khopt Kra’en

Terman Traits
Your character has certain abilities in common with all other termen.

Ability Score Increase. Charisma score increases by 1
Age. Most termen grow slowly. They are not considered adults until age 30, and may live over 300 years.  Some kings and queens have been known to live to be 500 or more. The exception to this is termen workers, who are mature by age 15 and rarely live more than 100 years.
Size. Termen workers are small, between 3 and 4 feet tall and less than 40 pounds. All other castes are Medium, between four and a half and five and a half feet tall and slim of build.
Speed. Your walking speed is 25 feet
Chitin. Termen have +1 to armor class due to their hardened cuticle

Multiple limbs.
Termen have four arms. Each arm is strong enough to wield a light weapon on it's own, but they have to use two arms for shields and other weapons. They need all four arms to wield a weapon with the Heavy or Two-handed property.
When they wield a weapon with the Versatile property they can use the damage value in parentheses. When Termen engage in Two-weapon fighting, they can use melee weapons wielded in one or two hands.

Gut microbes. The delicate balance of gut microbes renders them at disadvantage to saves vs consumed poisons.

Trophallaxis.  You may cast the spell Goodberry as a first level spell 1/day. This represents the advantagious microbes you can cough up and share with others or spread on your own wounds as a healing poultice.
Temptation of wood. Your culture dictates that you may not own items made of wood unless covered in metal or leather.  It is just too hard to keep from nibbling on them.

Antennae.  You gain proficiency in perception for checks involving scent or vibration (not vision) Blindsight. 20ft

Languages. Common, Dwarven

Castes
Born of magic, the strict castes that define terman society are all defined by the arcane. The castes of termen are as different in appearance and ability as the subraces of other cultures.

~~Terman Alchemist [Wizard] are perhaps the finest makers of potions among all of the races.  Their antipathy for elves has made termen hesitant to learn the classical schools of magic, and their alliance with dwarves did little to spread a culture of learned spell casters among them. But the natural reliance of their termite ancestor’s on germ lines of internal symbionts has resulted in the uncanny ability of some termen to combine the properties of extracts and harness microbes to produce magical effects.  The natural skill of social insects with complex systems makes them master manipulators of the magic properties of certain crystals.  They can be respected as great healers, but most often they are feared for their warping of microbes to produce spell-effects like the dreaded Contageon or harness all but invisible phages to Disintegrate the hardest of substances.

Intelligence +1

Size: Medium

~~Termidon or Termen Defenders [Eldritch Knight] pride themselves on their physical prowess and skill with weapons, but they hold well executed attacks with the spell-like abilities in the highest esteem.  They strive for efficient, not showy, means of destroying the enemies of their hive.  They make use of auto-alchemy to alter their biology. This caste possesses a feature unique among termen, a glandular opening in the middle of the forehead above the eyes.  As they rise in levels they learn to produce a variety of acids, adhesives, poisons, and gasses.

Constitution +1

Size: Medium

~~Tocsins [Bard] are the heralds of terman society, jovial and wise.  Sound is the glue that holds a hive together. Hive songs sooth or alarm a colony, and spread information.  When danger threatens, the sonic ability of a Tocsin can be a terrible weapon. 

Intelligence +1

Size: Medium

~~Swarm Lords [Druid] keep the hive clear of vermin, often by enlisting the aid of creatures to fight by their side. Because they have such strong ties to their primal nature, they have been known to change their very shape to that of the creatures that share their warrens.  The most powerful Swarm Lords can disassociate into the form of the deadliest swarms. This primal bond makes them unpredictable and quick to anger. 

Wisdom +1

Size: Medium

 ~~Theros [Ranger] scout far flung tunnel systems with their insect compaions for threats from the outside world.

Strength +1

Size: Medium

~~Terrarch [Cleric/Earth] are the most important element in terman society after the Queen and King.  They are responsible for directing hordes of common termen, wielding powerful earth magic in the excavation and construction of the nest.  Their pride of place often shows in their arrogance, but they are natural leaders and skilled at commanding groups.

Wisdom +1

Size: Medium

~~Slavers (Rogues, Assasins) catch members of other races and intelligent monsters.  They make use of various fungal extracts and poisons to charm them to augment the workforce and military of the colony.

Dexterity +1

Size: Medium

~~Archons or Royal Termen [Paladin] are the heart of any colony.  Princes and Princesses are the caste most likely encountered in the outside world. They are regulary cast out from their birth colonies to prove themselves before attracting a retinue and either starting a new colony or competing for the chance to lead and established colony.  Sometimes the most heroic members of the other castes can become Royal Termen and lead colonies if they gain a reputation for greatness and attract followers. It is the hope of all exceptional Termen to someday rule a colony, but only the best will make it.  The character of a colony is often dictated by the personality of its king.

Charisma +1

Size: Medium

~~Minions or Workers (Rogues) are physically small, but perform most of the day to day functions within a colony. They are integral to everything from construction and maintenance, to defense.

Advanced Tremor Sense: By tapping on a solid surface for 15 minutes with antennae, workers can "see" in an area describes by a cone (10' long x 5' high).  They can only visualize what is physically connected to the solid surface (they miss the beholders!)

Dexterity +1
Size: Small

~~Metal Smith [Fighter] are outcasts among their own kind.  While all termen benefit from the products of metallurgy, the scents and sounds are so off-putting that smithies can only be found in the outskirts of colonies.  Many are counted as dwarf-friends, and as a group have come to resemble their dwarven tutors to better implement their techniques.  Although they are not regarded as innovative by even dwarf standards, their attention to minute details and ability to integrate crystalline or organic elements into their work is highly respected.  Just don't expect wooden hafted weapons!

Strength +1

Size: Medium

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Arch-enemies!  Termen-vs-Formians

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