Pillar of Origins

As Pillar of Origins enters, choose a creature type.
{T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type.

Harmonic Sliver

All Slivers have "When this permanent enters, destroy target artifact or enchantment."

Bonescythe Sliver

Sliver creatures you control have double strike. (They deal both first-strike and regular combat damage.)

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Necrotic Sliver

All Slivers have "{3}, Sacrifice this permanent: Destroy target permanent."

Taunting Sliver

Sliver creatures you control have "When this creature enters, goad target creature an opponent controls." (Until your next turn, that creature attacks each combat if able and attacks a player other than you if able.)

Blur Sliver

Sliver creatures you control have haste. (They can attack and {T} as soon as they come under your control.)