Goboto , The Scrap Treasure

Trample
This spell costs {2} less to cast for each artifact or creature you’ve sacrificed this turn.
{1}{x}: target artifact you control gains Junkyard X,
X can't larger than the mana value of the target artifact.
(Junkyard X:When this permanent goes to the graveyard from the battlefield return other target artifact with mana value x or less to the battlefield)