Need help for my homebrew

[Muppet]

(Hi this is my first time posting so go easy on me)

I really need help creating an insanity system for a psionic subclass I’m making for the blood hunter called the order of the fractured mind. The idea is that at third level because of the mental strain of fighting monsters take its toll, their mind breaks unlocking latent psionic abilities, and during this fevered and broken state a blood hunter with this subclass figures out how to corrupt their curses to make the amplification even more powerful, but at an even greater cost to their health as well as their sanity, the problem is though I’m finding it difficult to think of a fleshed out insanity system or table to tie in with this ability in order to make it balanced.
Does anyone have any ideas?

[Schattenbach]

You could use inspirations from the already existing D20 Sanity systems, like, among other things, Pathfinders (http://www.d20pfsrd.com/gamemastering/other-rules/sanity/) sanity system or the standard Call Of Cthulhu-based Sanity System from the DnD3.5 SRD Sanity System (http://www.d20srd.org/srd/variant/campaigns/sanity.htm). You could also adopt the standard interpretation (as used in DnD3.0/Dnd3.5/DnD3.P) of various reduced Mental Ability Scores (Wisdom in particular) potentially also signifying becoming slowly insane (with several sanity-harming abilities, like those of the epic uvuudaum (http://www.d20srd.org/srd/epic/monsters/uvuudaum.htm), causing mental ability damage to represent a loss of sanity) or indeed has the outright risk to cause this as per pathfinder "Sanity and Madness" rules (http://legacy.aonprd.com/gameMasteryGuide/sanityAndMadness.html).

Maybe this helps.

Edit: I don’t remember if the Uvuudaum’s attacks or the horrible truths about reality - according to fluff I don’t remember in detail - that it enjoys whispering into peoples ears was the major source of its insanity-causing capabilities, maybe it was the was the later ... either way, using Mental Ability scores this way seems to work quite fine in and itself if one wants to avoid excessive bookkeeping.

[Vogie]

If you want non-recoverable sanity, you could co-opt something akin to the Dread system... that is, the sanity is represented by a Jenga tower, and each time they face a sanity hit, a block is removed. When the tower falls, that mind is gone...

[Stan]

If you want something that taps into current rules, you could have increases in psionic abilty be accompanied by giving a +1 icnrease to Int (or other score) and -1 penalty to Wisdom. With 5e's ability cap, the Int bonuses become less useful but the Wis reductions are going to impair the character.

Also look in the DMG for how it handles a sanity score and it's listing of conditions.