Thran Excavation Site

Thran Excavation Site enters the battlefield tapped.
{t}: Add{c}
{4},{t}: Conjure a card into your hand. Activate only
as a sorcery:
-Artificer's Dragon, Platoon Dispenser, Terror Ballista, Surge Engine, Perennial Behemoth
-Pardic Wanderer, Reconstructed Thopter, Su-Chi
Cave Guard, Thran Spider, Thran Power Suit
-Thran Portal, Hall of Tagsin, Damping Sphere, Defense Grid, Mesmeric Orb