Card

Eidolon of Rhetoric

Mana cost {2}{W}

Each player can't cast more than one spell each turn.

Part of 3 known combos, 3 of them two-card. 1 official ruling.

Bracket

B1 Exhibition — Not in the same deck as its two-card combo partners: Knowledge Pool, Possibility Storm, Erayo, Soratami Ascendant // Erayo's Essence
B2 Core — Not in the same deck as its two-card combo partners: Knowledge Pool, Possibility Storm, Erayo, Soratami Ascendant // Erayo's Essence
B3 Upgraded — Not in the same deck as its early two-card combo partners: Knowledge Pool, Possibility Storm
B4 Optimized — allowed: No restriction beyond the banned list
B5 cEDH — allowed: No restriction beyond the banned list

Two-card combo with Knowledge Pool, Possibility Storm, Erayo, Soratami Ascendant // Erayo's Essence (early with Knowledge Pool, Possibility Storm)

Bracket: Lotus Vault analysis, with Commander Spellbook flags

3 known combos, 3 of them two-card.

Knowledge Pool + Eidolon of Rhetoric
Produces: Exile all spells players cast from their hand, Players can only cast one spell per turn, Lock
View on Commander Spellbook
Eidolon of Rhetoric + Possibility Storm
Produces: Lock, Players can't cast spells from their hand
View on Commander Spellbook
Erayo, Soratami Ascendant // Erayo's Essence + Eidolon of Rhetoric
Produces: Opponents can't resolve any spell for the rest of the game, Lock
View on Commander Spellbook

2014-04-26 · Wizards of the Coast
Eidolon of Rhetoric will look at the entire turn to see if a player has cast a spell yet that turn, even if Eidolon of Rhetoric wasn't on the battlefield when that spell was cast. Specifically, you can't cast Eidolon of Rhetoric and then cast another spell that turn.

Rulings: Scryfall · Wizards of the Coast