Wound Reflection

At the beginning of each end step, each opponent loses life equal to the life they lost this turn. (Damage causes loss of life.)

Kaervek the Merciless

Whenever an opponent casts a spell, Kaervek the Merciless deals damage equal to that spell's mana value to any target.

{T}: Heartless Hidetsugu deals damage to each player equal to half that player's life total, rounded down.

Whenever an opponent casts a spell, that player loses 5 life unless they discard a card.