Card

Vexing Bauble

Mana cost {1}

Whenever a player casts a spell, if no mana was spent to cast it, counter that spell. {1}, {T}, Sacrifice this artifact: Draw a card.

Part of 6 known combos, 5 of them two-card. 2 official rulings.

Bracket

B1 Exhibition — Not in the same deck as its two-card combo partners: Knowledge Pool, Possibility Storm, Omen Machine, Guile, Eye of the Storm
B2 Core — Not in the same deck as its two-card combo partners: Knowledge Pool, Possibility Storm, Omen Machine, Guile, Eye of the Storm
B3 Upgraded — Not in the same deck as its early two-card combo partners: Knowledge Pool, Possibility Storm, Omen Machine, Eye of the 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, Omen Machine, Guile, Eye of the Storm (early with Knowledge Pool, Possibility Storm, Omen Machine, Eye of the Storm)

Bracket: Lotus Vault analysis, with Commander Spellbook flags

6 known combos, 5 of them two-card.

Noctis, Prince of Lucis + Aetherflux Reservoir + Vexing Bauble
Produces: Infinite damage, Infinite lifegain triggers, Infinite lifegain
View on Commander Spellbook
Vexing Bauble + Knowledge Pool
Produces: Counter all spells players cast from their hands, Lock
View on Commander Spellbook
Vexing Bauble + Possibility Storm
Produces: Counter all spells players cast from their hands, Lock
View on Commander Spellbook

2024-06-07 · Wizards of the Coast
If a spell is cast with an alternative cost that includes mana (such as flashback), Vexing Bauble's first ability won't trigger and won't counter that spell. Similarly, if a spell is cast without paying its mana cost, but the player did pay mana for additional costs such as from kicker or from Thorn of Amethyst, Vexing Bauble's first ability won't trigger and won't counter that spell.
2024-06-07 · Wizards of the Coast
Players may cast spells that they know Vexing Bauble will counter. Any abilities that trigger when spells are cast will still trigger and resolve if appropriate, and any effects that count how many spells are cast will still count those spells if appropriate.

Rulings: Scryfall · Wizards of the Coast