Ancient Den

Fellwar Stone

{T}: Add one mana of any color that a land an opponent controls could produce.

Plains

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice Mind Stone: Draw a card.

Sanctum Spirit

Lifelink
Discard a historic card: Sanctum Spirit gains indestructible until end of turn. (Artifacts, legendaries, and Sagas are historic.)

Leonin Squire

When Leonin Squire enters the battlefield, return target artifact card with mana value 1 or less from your graveyard to your hand.

Darksteel Citadel

Mine Excavation

Return target artifact or enchantment card from a graveyard to its owner's hand.
Conspire (As you cast this spell, you may tap two untapped creatures you control that share a color with it. When you do, copy it and you may choose a new target for the copy.)

Guardian Idol

Guardian Idol enters the battlefield tapped.
{T}: Add {C}.
{2}: Guardian Idol becomes a 2/2 Golem artifact creature until end of turn.