Goblin Haggler

Whenever Goblin Haggler deals combat damage to a
player, you may cast a goblin spell from your hand
without paying its mana cost unless that player gives
you control of an artifact or land.

Dash {r}{r} (You may cast this spell for its dash cost.
If you do, it gains haste, and it's returned from the
battlefield to its owner's hand at the beginning of the
next end step.)