Sidekick rules

Humanity and other races are made up of mostly zero level creatures, but there are 2 other types: Fixed and Levelers. A Fixed being starts at a random level (usually 2 d4 (on a 4, add 4, then re-roll that die, up to the limit of the campaign setting)) and stays at that level forever. Levers started at level 1 (2 if PCs) and have the potential to go up in level, giving greater stats and more ability slots through Experience points. Experience points (or XP) are gained through training and killing monsters, as well as consuming Mana Crystals. Fixed do not gain experience points or level up. Sidekicks are a loophole in these rules.  A Leveler shares some of the experience that enters their body with another being they have bonded with. The bonding is an 8hr ceremony that can take place during a long rest. The Lever can then send a portion of their EP total, that hasn't been used to level themselves up to the sidekick. 

Sidekicks follow the 3/3 rules. Regular NPCs are gone if not saved by next turned after being downed.

We will be using the Tasha's cauldron rules for sidekicks (pages 142 to 147) with the following changes. Whatever level they enter the story at is the level they will stay at. A PC can mentor a sidekick and funnel EP into the character to level it, alter stats (at first level) and be taught special abilities. Sidekicks can also be trained at the rate of 25exp per week (this training requires their mentor to be training with them).

Cost to level is from 0 to 1, 100exp, 1 to 2 +200exp, 2 to 3 +400exp, 3 to 4 +800exp, 5 to 6 +1600exp, 7 to 8 +3200exp, etc. Hp at level zero is 1d4 (3Hp). Hit Dice for sidekicks is usually D6.

Cost to modify attributes +1d4 to an att is 100exp, +1d6 to an att is 200exp, +1d8 to an att is 400exp. Only 1 die per attribute and only at 1st level. If the mentor is not satisficed with the roll they can reroll for the same exp cost and keep the higher roll. (optional: Attribute modification for sidekicks at levels 2+, multiple the cost by level, so +1d6 at level 4 is 800exp per roll).

Cost to learn a special ability depends of the cost the PC paid to learn it. Sidekicks can't teach special ability.