Card

Magistrate's Scepter

Mana cost {3}

{4}, {T}: Put a charge counter on this artifact. {T}, Remove three charge counters from this artifact: Take an extra turn after this one.

Extra-turn card: not allowed in brackets 1–2, two at most in bracket 3. Part of 194 known combos, 8 of them two-card. 1 official ruling.

Bracket

B1 Exhibition — not allowed: Extra-turn cards are not allowed
B2 Core — not allowed: Extra-turn cards are not allowed
B3 Upgraded — Not in the same deck as its early two-card combo partners: Clock of Omens, Aetheric Amplifier, Ichormoon Gauntlet, Vorel of the Hull Clade, Viral Drake, Lulu, Stern Guardian, Gogo, Master of Mimicry, Merfolk Skydiver
B4 Optimized — allowed: No restriction beyond the banned list
B5 cEDH — allowed: No restriction beyond the banned list

Extra-turn card, two at most in bracket 3 (Lotus Vault house cap)
Two-card combo with Clock of Omens, Aetheric Amplifier, Ichormoon Gauntlet, Vorel of the Hull Clade, Viral Drake, Lulu, Stern Guardian, Gogo, Master of Mimicry, Merfolk Skydiver (early with Clock of Omens, Aetheric Amplifier, Ichormoon Gauntlet, Vorel of the Hull Clade, Viral Drake, Lulu, Stern Guardian, Gogo, Master of Mimicry, Merfolk Skydiver)

Bracket: Lotus Vault analysis, with Commander Spellbook flags

194 known combos, 8 of them two-card.

2018-07-13 · Wizards of the Coast
If multiple extra turns would be taken after this one, perhaps because more than one player has activated the last ability of their Magistrate’s Scepter, the most recently created one is taken first.

Rulings: Scryfall · Wizards of the Coast