Volk, Collector of Tools

Artifacts on the battlefield and in all hands have
sell 2 (Exile this card to Volk, Collector of Tools, then create two Gold artifact tokens with "Sacrifice this
artifact: Add one mana of any color to your mana
pool." Sell only as a sorcery.).
Artifacts exiled by Volk have purchase 4 (Cards
with purchase may only be cast by sacrificing Gold or Treasure tokens equal to its purchase cost. Any player
may cast a spell with purchase except whoever sold it.).