Bloodied

One of my favourite rules from 4e, and one of the ones I was most sad to see go in 5e, was the Bloodied condition. This was basically a shorthand that indicated that the character or monster had been reduced to half hit points - it was also the point at which the creature was visibly weakened by the punishment that it had taken.

This is still a term I make extensive use of in my D&D games, as it remains useful.

But one of the things I particularly liked about the Bloodied condition, and something that is harder to build in on an ad hoc basis, was those few cases where Bloodied had an actual effect - perhaps a monster would lose access to some particular weapon when Bloodied (as an arm is severed)... or perhaps they become more powerful as they become more desperate. And, conversely, perhaps a monster enters a berserk rage when fighting an opponent that has become Bloodied.

I do like those effects, and I do try to build them into 'significant' monsters that I build. Anything to make combats, and especially longer combats, more than just a slog of hit point attrition!