Thought-Knot Seer

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

Urza's Tower

{T}: Add {C}. If you control an Urza's Mine and an Urza's Power-Plant, add {C}{C}{C} instead.

Forest

Enter the Unknown

Target creature you control explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on the creature, then put the card back or put it into your graveyard.)
You may play an additional land this turn.

Hand of Emrakul

You may sacrifice four Eldrazi Spawn rather than pay this spell's mana cost.
Annihilator 1 (Whenever this creature attacks, defending player sacrifices a permanent of their choice.)

All Is Dust

Each player sacrifices all permanents they control that are one or more colors.

Skittering Invasion

Create five 0/1 colorless Eldrazi Spawn creature tokens. They have "Sacrifice this token: Add {C}."

Kozilek's Command

Choose two —
• Target player creates X 0/1 colorless Eldrazi Spawn creature tokens with "Sacrifice this token: Add {C}."
• Target player scries X, then draws a card.
• Exile target creature with mana value X or less.
• Exile up to X target cards from graveyards.

Glaring Fleshraker

Whenever you cast a colorless spell, create a 0/1 colorless Eldrazi Spawn creature token with "Sacrifice this token: Add {C}."
Whenever another colorless creature you control enters, this creature deals 1 damage to each opponent.

Kozilek's Predator

When this creature enters, create two 0/1 colorless Eldrazi Spawn creature tokens. They have "Sacrifice this token: Add {C}."

Explore

You may play an additional land this turn.
Draw a card.

Broodwarden

Eldrazi Spawn creatures you control get +2/+1.

Urza's Mine

{T}: Add {C}. If you control an Urza's Power-Plant and an Urza's Tower, add {C}{C} instead.

Urza's Power Plant

{T}: Add {C}. If you control an Urza's Mine and an Urza's Tower, add {C}{C} instead.