Aluren

Any player may cast creature spells with mana value 3 or less without paying their mana costs and as though they had flash.

Squee, the Immortal

You may cast Squee, the Immortal from your graveyard or from exile.

Goblin Bombardment

Sacrifice a creature: Goblin Bombardment deals 1 damage to any target.

Food Chain

Exile a creature you control: Add X mana of any one color, where X is 1 plus the exiled creature's mana value. Spend this mana only to cast creature spells.

Phyrexian Altar

Sacrifice a creature: Add one mana of any color.

Ashnod's Altar

Eternal Scourge

You may cast Eternal Scourge from exile.
When Eternal Scourge becomes the target of a spell or ability an opponent controls, exile Eternal Scourge.