Card

Mazirek, Kraul Death Priest

Mana cost {3}{B}{G}

Flying Whenever a player sacrifices another permanent, put a +1/+1 counter on each creature you control.

Part of 35 known combos, one of them two-card. 4 official rulings.

Bracket

B1 Exhibition — Not in the same deck as its two-card combo partner: Basking Broodscale
B2 Core — Not in the same deck as its two-card combo partner: Basking Broodscale
B3 Upgraded — Not in the same deck as its early two-card combo partner: Basking Broodscale
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

35 known combos, one of them two-card.

Basking Broodscale + Mazirek, Kraul Death Priest
Produces: Infinite colorless mana, Infinite death triggers, Infinite creature ETB
View on Commander Spellbook
Mazirek, Kraul Death Priest + Scurry Oak + Ashnod's Altar
Produces: Infinite colorless mana, Infinite death triggers, Infinite creature ETB
View on Commander Spellbook
Ghave, Guru of Spores + Mazirek, Kraul Death Priest + Ashnod's Altar
Produces: Infinite colorless mana, Infinite creature tokens, Infinite death triggers
View on Commander Spellbook

2020-08-07 · Wizards of the Coast
If you sacrifice Mazirek and other permanents at the same time, Mazirek's last ability triggers for the other permanents.
2020-08-07 · Wizards of the Coast
If you sacrifice a permanent as part of casting a spell or activating an ability, Mazirek's last ability will resolve before that spell or ability.
2020-08-07 · Wizards of the Coast
Mazirek's last ability is a triggered ability, not an activated ability. It doesn't allow you to sacrifice a permanent whenever you want; rather, you need some other way of sacrificing permanents.
2020-08-07 · Wizards of the Coast
A legendary permanent that is put into a graveyard because of the "legend rule" isn't sacrificed.

Rulings: Scryfall · Wizards of the Coast