Death's Shadow

This creature gets -X/-X, where X is your life total.

Abigale, Eloquent First-Year

Flying, first strike, lifelink
When Abigale enters, up to one other target creature loses all abilities. Put a flying counter, a first strike counter, and a lifelink counter on that creature.

Cecil, Redeemed Paladin

Lifelink
Protect — Whenever Cecil attacks, other attacking creatures gain indestructible until end of turn.

Cecil, Dark Knight

Deathtouch
Darkness — Whenever Cecil deals damage, you lose that much life. Then if your life total is less than or equal to half your starting life total, untap Cecil and transform it.