Running on the batteries as health idea )get it, running on?) a Tainted version could maybe have the same cocnept, but instead it "steals" this energy from enemies to recharge itself using a special item liek a plug of sorts to stick to enemis and steal from them to charge yourself or your item and tat's your only way of charing.
A tarnished i am not sure,but maybe you instead run on "rechargable batteries", and you need to wait a bit after cleairng a room to maybe use items or something of the sort, and you have a "low power", "sufifciently powered" and "full power" modes depending on your charge that affects your tears and stats

what if the gimmick is that he can only be healed via batteries (and making batteries more common of course)

the birthright should give you a molten brain-worm

please add unlocks!

Your health and item use meter are linked, you can use powerful charged items all the time but each use drains hp, and aside from batteries supercharging you can only have 3 charges/health with an extra 3 acting as soul hearts

How about for a gimmick theres a power generator in a room on the floor, which you need to find to recharge yourself?
You *can* proceed without charge, but being in lower power mode will make you much weaker, lowing your fire rate, damage, and luck.

what if, you run on batteries?
Like, your health is batteries, or even for the tainted version, you had to keep sucking out an active items charge every like, ten to six rooms to stay on, like your practically immortal, but you need to keep a charge or you just straight up fucking die!
Ya' know?

How about for a gimmick, you can recharge active items using red heart pickups when red health is full or you don't have red health at all?