I’ve not been able to find an exact answer for this, but what exactly does an ability that leaves an opponent bleeding do? Best guess is that they continue to lose health points even when they’re not being targeted for attacks? Sorry if it’s a dumb question, I just couldn’t find an exact description of it.
I can only assume you’re referring to Elektra’s red ability?
Basically she creates a red trap tile on the board. As long as that trap tile exists, it’ll do X amount of damage to the character in front. The trap tile is hidden from the opponent.
If you’re not talking about that…I can only assume you’re on the wrong board, maybe? =P
It’s really a legacy thing from the older fantasy-themed Puzzle Quest games. Black tends to be a colour for abilities that cause a “bleeding” or a “poisoned” effect that drains your opponent’s health every turn, which is basically what attack tiles do. You can see that many of the older characters will generate attack tiles from their black abilities, like Storm, Punisher and Psylocke.