Card

Havoc Jester

Mana cost {4}{R}

Whenever you sacrifice a permanent, this creature deals 1 damage to any target.

Part of 732 known combos, 2 of them two-card. 4 official rulings.

Bracket

B1 Exhibition — Not in the same deck as its two-card combo partners: Smaug the Impenetrable, Magmatic Galleon
B2 Core — Not in the same deck as its two-card combo partners: Smaug the Impenetrable, Magmatic Galleon
B3 Upgraded — Not in the same deck as its early two-card combo partners: Smaug the Impenetrable, Magmatic Galleon
B4 Optimized — allowed: No restriction beyond the banned list
B5 cEDH — allowed: No restriction beyond the banned list

Two-card combo with Smaug the Impenetrable, Magmatic Galleon (early with Smaug the Impenetrable, Magmatic Galleon)

Bracket: Lotus Vault analysis, with Commander Spellbook flags

732 known combos, 2 of them two-card.

2020-06-23 · Wizards of the Coast
Havoc Jester's ability triggers when you sacrifice it. If you sacrifice other permanents at the same time, it triggers for them as well.
2020-06-23 · Wizards of the Coast
If you sacrifice a permanent as part of casting a spell or activating an ability, Havoc Jester's ability will resolve before that spell or ability.
2020-06-23 · Wizards of the Coast
Havoc Jester's 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.
2020-06-23 · 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