Myr Reservoir is a rare Artifact card from Scars of Mirrodin (SOM), collector number 183. Current market price: $2.48 (foil $4.18), TCGplayer market prices via Scryfall.
{T}: Add {C}{C}. Spend this mana only to cast Myr spells or activate abilities of Myr. {3}, {T}: Return target Myr card from your graveyard to your hand.