1B
Destroy target attacking creature. Gain 3 life.

And that's it at its weakest ignoring Stifles (So it still kills anything with 3 or less toughness without first strike) or the potential of just chumping a first striker (Or pro black I guess).

you sure about that

The defensive use is kind of weird, I might have liked it better if it specified "attacking knight" like Dire Fleet Poisoner.

Yes? I don’t get your meaning

Creatures with protection from black can't be blocked by black creatures.

Yeah so it's another fail state like having him as your only potential blocker when something with first strike attacks or when he's countered (though not necessarily when Stifled because it is still a 3/1 flash which is basically "Destroy target attacking creature" for the early game.