Panharmonicon [The List] Artifact Set: McDonald's Promos: 2016 Collection

Set: McDonald's Promos: 2016 Collection Type: Fairy Rarity: Promo Retreat cost: Colorless

and are often eager to share the dark knowledge they obtain with friendly adventurers

Set: Black & White: Dragons Exalted Type: Grass Rarity: Rare Retreat cost: Colorless

It's also a Sliver

Panharmonicon [The List] Artifact Set: McDonald's Promos: 2016 CollectionSet: The List Type: Artifact Rarity: Rare Cost: {4} If an artifact or creature entering the battlefield causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time. All who listen hear their own song, a unique melody played just for them.