Heartless Act

Choose one —
• Destroy target creature with no counters on it.
• Remove up to three counters from target creature.

Bloodletter of Aclazotz

Flying
If an opponent would lose life during your turn, they lose twice that much life instead. (Damage causes loss of life.)

Lich

As this enchantment enters, you lose life equal to your life total.
You don't lose the game for having 0 or less life.
If you would gain life, draw that many cards instead.
Whenever you're dealt damage, sacrifice that many nontoken permanents. If you can't, you lose the game.
When this enchantment is put into a graveyard from the battlefield, you lose the game.

Magus of the Mirror

{T}, Sacrifice this creature: Exchange life totals with target opponent. Activate only during your upkeep.

Profane Transfusion

Two target players exchange life totals. You create an X/X colorless Horror artifact creature token, where X is the difference between those players' life totals.

Foggy Swamp Visions

As an additional cost to cast this spell, waterbend {X}. (While paying a waterbend cost, you can tap your artifacts and creatures to help. Each one pays for {1}.)
Exile X target creature cards from graveyards. For each creature card exiled this way, create a token that's a copy of it. At the beginning of your next end step, sacrifice those tokens.

Swamp

Soul Conduit

{6}, {T}: Two target players exchange life totals.

Fire Lord Sozin

Menace, firebending 3 (Whenever this creature attacks, add {R}{R}{R}. This mana lasts until end of combat.)
Whenever Fire Lord Sozin deals combat damage to a player, you may pay {X}. When you do, put any number of target creature cards with total mana value X or less from that player's graveyard onto the battlefield under your control.

The Rise of Sozin

(As this Saga enters and after your draw step, add a lore counter.)
I — Destroy all creatures.
II — Choose a card name. Search target opponent's graveyard, hand, and library for up to four cards with that name and exile them. Then that player shuffles.
III — Exile this Saga, then return it to the battlefield transformed under your control.

The Rise of Sozin // Fire Lord Sozin

Mai, Scornful Striker

First strike
Whenever a player casts a noncreature spell, they lose 2 life.

Pact Weapon

As long as this Equipment is attached to a creature, you don't lose the game for having 0 or less life.
Whenever equipped creature attacks, draw a card and reveal it. The creature gets +X/+X until end of turn and you lose X life, where X is that card's mana value.
Equip—Discard a card.

Azula, On the Hunt

Firebending 2 (Whenever this creature attacks, add {R}{R}. This mana lasts until end of combat.)
Whenever Azula attacks, you lose 1 life and create a Clue token. (It's an artifact with "{2}, Sacrifice this token: Draw a card.")