Hedron Detonator is a rare Creature — Goblin Artificer card from March of the Machine Commander (MOC), collector number 118. Current market price: $7.75, TCGplayer market prices via Scryfall.
Whenever an artifact you control enters, this creature deals 1 damage to target opponent. {T}, Sacrifice two artifacts: Exile the top card of your library. You may play that card this turn.