Ulduar

Ulduar enters the battlefield tapped.
{t}: Add {c}{c}{c} to your mana pool if you control 5 or more Artifacts.
{c}{c}{c}{c}{c}{c}{c}, {t}, Sacrifice Ulduar: Search your library for "Yogg'Saron, the Lucid Dream", reveal it, and add it to your hand. If 10 or more cards were exiled this turn, put it onto the battlefield.
Artifact spells you cast cost {1} less to cast.