Well I looked, and it seems no one decided to do the public a favor and include WHAT THE MOD DOES... so I will take the time to type it.

Derpkin: Looks like an insect. Press Z to leap to cursor. Press X to spin, gaining temporary invincibility. -20% HP | -20% Endurance | +20% Movement Speed | +30% Jump Speed

Dragonkin: Looks like a lizard-faced mage. Hold Z to breathe burning smoke, damage scales with defense. Press X to release a molotov fireball, damage also scales with defense.
+20% Endurance | -20% Movement Speed | -10% Jump Speed

Fluftrodon: looks like a gray humanoid dog with a beak. (My examinations of these sprites are terrible) Press Z to paint, left click and right click to paint tiles and walls, scroll to cycle color. Hold X to charge up a powerful leap, scales with max health. Hold A or D against a wall and press space to walljump, scales with max health.
-14% Damage | -25% Mining Delay | +50% Tile Placement Speed | +10% Tile Placement Range

Goblin: Looks like a terraria goblin, need I go on? Press Z to shadowforge your held item, granting it unique powers, costs mana. Press X to unleash a shadowflame harvester, which burns enemies and grants you improved mana regeneration.
-20% HP | +40% MP | +1 Max Minion | +1 Max Sentry | +10% Movement Speed

Kenku: Looks like a humanoid bird with a shirt. While airborne, press Z to swoop forwards. Press X to fire a volley of feathers, fly within range of the feathers to launch yourself. You are equipped with natural wings by default, which power scales with max health. At above 160 max health, you no longer take fall damage.
-33% HP | -30% Endurance | +20% Movement Speed | +15% Jump Speed

Kobold: Looks like a humanoid dinosaur. Press Z to breathe out a sparkmine. Press X to fire a cluster of mines. Press C to detonate any mines within range, Clustermines have an unimited activation radius. Sunlight slows and weakens you.
-10% HP | -5% Endurance | +75% Mining Delay | +4% Movement Speed

Lizhard: Looks like a terraria Lizhard, but with better posture. Press Z to open a golem placing menu, scroll to cycle through selected golems, damage scales with defense. Hold X to crawl (and lose your good posture), allowing you to climb up walls and fit into small gaps. You lose defense and regeneration outside of the sun.
-50% Damage (ouch) | -30% Mining Delay | +10% Tile Placement Speed

Lycan: Looks more like a gray humanoid dog than the Fluftrodon. Hold Z to record time, let go to rewind time, rewinding all nearby entities to their previous locations. Hold X to replay your last rewound timeline, let go to teleport to the current position in the replay.
+10% Endurance | +14% Damage | -10% Tile Placement Speed | -10% Wall Placement Speed | +15% Movement Speed | +5% Jump Speed

Merfolk: Looks like a slightly altered mer-person that you become using the Neptune's Shell. While underwater, hold Z to streamline-swim, which improves control and speed. While underwater, press X to kick forward for a boost of momentum.
-10% Mining Delay | +10% Tile Placement Speed

Mushfolk: Looks like the Truffle NPC. Hold Z to release trapshroom spores, which release healing clouds upon contact with an enemy, healing scales with the individual's max health. Press X to create a Nymphshroom, which teleports you to it upon contact with an enemy.
+10% HP | -25% Endurance | -10% Damage | +4% Movement Speed

Skeleton: Looks like a dungeon skeleton that lost his neck. Press Z, X, and C to switch between bodies. When you die, your skeleton releases its spirit, if you can survive without being hit long enough, you reform a new skeleton and return to life.
-50% Endurance (again, ouch) | +10% Damage | +15% Movement Speed

Tabaxi: Looks like a humanoid cat that can actually wear a full set of cosmetic clothing. Hold Z to charge up an intangible dash. Press X to rewind point, press C to return to it.
-10% Endurance | -15% Critical Strike Chance | -15% Mining Delay | +15% Movement Speed | +10% Jump Speed

Vampire: Looks like... something. It is very hard to describe, but I think it looks like a black skull with a dark body. Press Z to transform into a bat. You enter stealth after a few seconds, making enemies ignore you. Press X while in batform to release an abnormally long tongue, which latches onto enemies and drains an extremely small amount of health. You cannot use healing potions (RIP). Getting attacked under the sun sets you on fire.
-25% HP | -15% Endurance | +10% Movement Speed

Wendigo: Looks like a dark humanoid dog, but its skull and ribcage is showing. Hold Z to tear through reality, turning you into an intangible missile, maximum duration scales with max health. Hold X to attack with your claws, shredding enemy defense, damage scales with max health. (The range makes it extremely risky to use against dungeon guardian, in case that was in your mind.)
-10% Endurance | +14% Damage | +25% Movement Speed

That concludes the information that should really be on a wiki somewhere. Some characters are broken, some are almost useless. To whoever is reading this, have a good day actually knowing the forbidden knowledge that cannot be found anywhere on the internet.

(I hope this discussion will get the mod more popularity)

(Edit: There is now a wiki for this mod, thanks to Bellcat and me, so this discussion is kinda useless)