Eldrazi Temple

{T}: Add {C}.
{T}: Add {C}{C}. Spend this mana only to cast colorless Eldrazi spells or activate abilities of colorless Eldrazi.

Thought-Knot Seer

({C} represents colorless mana.)
When Thought-Knot Seer enters the battlefield, target opponent reveals their hand. You choose a nonland card from it and exile that card.
When Thought-Knot Seer leaves the battlefield, target opponent draws a card.

Eldrazi Mimic

Whenever another colorless creature enters the battlefield under your control, you may change Eldrazi Mimic's base power and toughness to that creature's power and toughness until end of turn.

Eldrazi Linebreaker

Devoid (This card has no color.)
Trample
At the beginning of combat on your turn, target creature you control gains haste and gets +X/+0 until end of turn, where X is the number of Eldrazi you control.

Ugin's Labyrinth

Imprint — When Ugin's Labyrinth enters the battlefield, you may exile a colorless card with mana value 7 or greater from your hand.
{T}: Add {C}. If a card is exiled with Ugin's Labyrinth, add {C}{C} instead.
{T}: Return the exiled card to its owner's hand.

It That Heralds the End

Colorless spells you cast with mana value 7 or greater cost {1} less to cast.
Other colorless creatures you control get +1/+1.