Your hit points are fixed to the size of your horde.  Your hit points are fixed as follows:

• Level 1-5:  [10 + your Constitution modifier] + [3 x (1d10 + your Constitution modifier)]
• Level 6-10: [10 + your Constitution modifier] + [8 x (1d10 + your Constitution modifier)]
• Level 11-15:  [10 + your Constitution modifier] + [13 x (1d10 + your Constitution modifier)]
• Level 15-20:  [10 + your Constitution modifier] + [18 x (1d10 + your Constitution modifier)]

All Aimians are effectively immortal due to their changeable and gestalt nature, but they can be killed.  They are considered adults after approximately 50 to 100 years of existence.

The Sleepless tend toward pragmatic neutrality.  Although not mortal, they defend life.  Though they are willing to kill in order to preserve it.  There are very few known Sleepless swarms on Roshar, the majority of Aimian choosing to become Siah Aimians to better fit in to mortal society.  They vote on important matters using the rapid communication provided by their hive minds and buzzing vibrational communication.

Your size begins as Medium. To set your height and weight randomly, start with rolling a size modifier:

• Size modifier = 2d8
• Height = 4 feet + 6 inches + your size modifier in inches
• Weight in pounds = 90 + (2d4 × your size modifier)

Individual hordelings that make up your body are usually about the size of a finger, but they can be as large as a fist.  Your size changes as you level and your swarm grows in number.

• Level 1-5 Medium
• Level 6-12 Large
• Level 13-20 Huge

As you lose hit points, individual members of your swarm die, reducing your total size one size down for every 25% hit points lost to a minimum of tiny. You must perform a short or long rest to replenish them via hordeling breeding.

• Walking speed of 30 feet (humanoid form only)
• Burrowing speed of 5 feet (swarm form only)
• Climbing speed of 15 feet (swarm form only)

Your hordelings don't require sleep.  When you take a long rest, you must spend at least four hours in a state of replenishment (hordeling breeding). In this state, you are not asleep, and you can see and hear as normal.

You can directly communicate with mortals and other Sleepless swarms using vibrational communication. This is achieved through buzzing that emanates from your hordelings themselves. This noise can form an approximate sound of language (in humanoid form only) or cacophonous droning that only another Sleepless swarm can understand.

While in humanoid form, you speak in Common and one other language of your choice.

While in swarm form, you can speak only by using your vibrational communication.

You cannot be charmed, healed by normal or magical means, or gain temporary hit points, and magic cannot put you to sleep.

+2 Constitution, +1 Choose an Ability Score

You gain proficiency with one of the following skills of your choice: Arcana, Perception, Survival.

You are deeply unsettling to most living creatures. If your face is uncovered or you are otherwise in plain view, you have disadvantage on Persuasion checks and advantage on Intimidation checks.

Rodents, insects, and other small creatures do not attack or flee from you on sight (unless magically compelled to do so). You have advantage on Animal Handling checks.

•  You can’t cast spells or speak a language, and your ability to take any action that requires hands is limited to the capabilities of your form.
• Transforming doesn’t break your concentration on a spell you’ve already cast or prevent you from taking actions that are part of a spell that you’ve already cast.
• You retain the benefit of any non-spellcasting features from your class, feats, or other sources and can use them if the new form is physically capable of doing so.
• Your equipment falls to the ground in your swarm’s space.
• You can move through any opening large enough for a single hordeling.
• Your hordelings can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.
• Difficult terrain does not cost extra movement.
• Gain a +4 bonus to Stealth Skill checks.
• Tremorsense. You can detect and pinpoint the origin of vibrations within 60 feet, provided that some part of you and the source of the vibrations are in contact with the same ground of substance.
• Immune to being Charmed, Grappled, Paralyzed, Petrified, Prone, Restrained, and Stunned.
• You cannot gain temporary hit points or regain hit points by normal or magical means.
• Pinch/Sting/Bite Attack. Melee Weapon Attack: Dex + Prof Bonus to hit, reach 0 feet. Effects all creatures in the swarm's space (including allies). If the swarm has half hit points or fewer, it deals half the damage.
  • Level 1-5: 1d6 + Con Bonus Piercing Damage
  • Level 6-12: 2d6 + Con Bonus Piercing Damage
  • Level 13-20: 3d6 + Con Bonus Piercing Damage

• You cannot gain temporary hit points.
• Your hordelings are not limited in how they assemble themselves. With practice and proper selective breeding, you can mimic the shape of any other creature that you have seen.  However, you do not gain the attributes of that creature.
• Damage and conditions suffered in swarm form remain when you return to humanoid form.
• You can cast spells, speak languages in a buzzing manner, use armor and weapons, and benefit from all features from your class, feats, or other sources