Emry, Lurker of the Loch

Once you announce that you're casting a spell, no player may take actions until the spell has been paid for. Notably, opponents can't try to change by how much Emry's cost is reduced.

You must follow the normal timing permissions and restrictions for the target artifact card. Unless it has flash, you'll most likely only be able to cast it during your main phase while the stack is empty.

Casting the target card causes it to leave your graveyard and become a new object. You can't cast it again if it returns to your graveyard this turn.