Card

Kaervek, the Spiteful

Mana cost {2}{B}{B}

Other creatures get -1/-1.

Part of 28 known combos, one of them two-card. 2 official rulings.

Bracket

B1 Exhibition — Not in the same deck as its two-card combo partner: Godhead of Awe
B2 Core — Not in the same deck as its two-card combo partner: Godhead of Awe
B3 Upgraded — Not in the same deck as its early two-card combo partner: Godhead of Awe
B4 Optimized — allowed: No restriction beyond the banned list
B5 cEDH — allowed: No restriction beyond the banned list

Bracket: Lotus Vault analysis, with Commander Spellbook flags

28 known combos, one of them two-card.

Kormus Bell + Urborg, Tomb of Yawgmoth + Kaervek, the Spiteful
Produces: Destroy all lands, Destroy all lands that enter the battlefield, Lock
View on Commander Spellbook
Kaervek, the Spiteful + Gravecrawler + Pitiless Plunderer
Produces: Infinite death triggers, Infinite creature ETB, Infinite creature LTB
View on Commander Spellbook
Vhati il-Dal + Thornbite Staff + Kaervek, the Spiteful
Produces: Destroy any number of creatures, Destroy each creature that enters the battlefield under an opponent's control, Lock
View on Commander Spellbook

2020-06-23 · Wizards of the Coast
Because damage remains marked on a creature until the damage is removed as the turn ends, nonlethal damage dealt to creatures may become lethal if Kaervek enters the battlefield during that turn.
2020-06-23 · Wizards of the Coast
If you control more than one Kaervek, each will give each other creature -1/-1. If these effects cause a creature's toughness to become less than or equal to 0 or the amount of damage marked on it, those creatures die at the same time that the “legend rule” remove your excess Kaerveks.

Rulings: Scryfall · Wizards of the Coast