Card

Grinning Ignus

Mana cost {2}{R}

{R}, Return this creature to its owner's hand: Add {C}{C}{R}. Activate only as a sorcery.

Part of 95 known combos, 7 of them two-card. 4 official rulings.

Bracket

B1 Exhibition — Not in the same deck as its two-card combo partners: Birgi, God of Storytelling // Harnfel, Horn of Bounty, Runaway Steam-Kin, Marvin, Murderous Mimic, The Vision and Scarlet Witch, Aluren, Morophon, the Boundless, Earthcraft
B2 Core — Not in the same deck as its two-card combo partners: Birgi, God of Storytelling // Harnfel, Horn of Bounty, Runaway Steam-Kin, Marvin, Murderous Mimic, The Vision and Scarlet Witch, Aluren, Morophon, the Boundless, Earthcraft
B3 Upgraded — Not in the same deck as its early two-card combo partners: The Vision and Scarlet Witch, Aluren
B4 Optimized — allowed: No restriction beyond the banned list
B5 cEDH — allowed: No restriction beyond the banned list

Two-card combo with Birgi, God of Storytelling // Harnfel, Horn of Bounty, Runaway Steam-Kin, Marvin, Murderous Mimic, The Vision and Scarlet Witch, Aluren, Morophon, the Boundless, Earthcraft (early with The Vision and Scarlet Witch, Aluren)

Bracket: Lotus Vault analysis, with Commander Spellbook flags

95 known combos, 7 of them two-card.

Birgi, God of Storytelling // Harnfel, Horn of Bounty + Grinning Ignus
Produces: Infinite creature ETB, Infinite creature LTB, Infinite storm count
View on Commander Spellbook
Grinning Ignus + Runaway Steam-Kin
Produces: Infinite creature ETB, Infinite creature LTB, Infinite storm count
View on Commander Spellbook
Treasonous Ogre + Aetherflux Reservoir + Grinning Ignus
Produces: Infinite damage, Infinite creature ETB, Infinite lifegain
View on Commander Spellbook

2021-04-16 · Wizards of the Coast
If you cast this as normal during your main phase, it will enter the battlefield and you'll receive priority. If no abilities trigger because of this, you can activate its ability immediately, before any other player has a chance to remove it from the battlefield.
2021-04-16 · Wizards of the Coast
Although Grinning Ignus's ability has a timing restriction, it's still a mana ability. It doesn't use the stack and it can't be responded to.
2021-03-19 · Wizards of the Coast
Although Grinning Ignus's ability has a timing restriction, it's still a mana ability. It doesn't use the stack and it can't be responded to.
2021-03-19 · Wizards of the Coast
If you cast Grinning Ignus during your main phase, it will enter the battlefield and you'll receive priority. If no abilities trigger because of this, you can activate its ability immediately, before any other player has a chance to remove it from the battlefield.

Rulings: Scryfall · Wizards of the Coast