Mana Echoes [Double Masters]Set: Double Masters Type: Enchantment Rarity: Mythic Cost: {2}{R}{R} Whenever a creature enters the battlefield, you may add an amount of {C} equal to the number of creatures you control that share a creature type with it. When the ground is saturated with mana, even the lightest footstep can bring it to the surface.

Set: League & Championship Cards Type: Trainer Rarity: Promo

Set: Sun & Moon: Guardians Rising Type: Special Colorless Energy Rarity: Secret Rare

If it's a 'non-attack' action card

Set: EX: Dragon Type: Psychic Rarity: Holo Rare Retreat cost: Colorless

"One beginning

Set: Eldritch Moon Type: Legendary Creature — Angel Horror Rarity: Mythic Cost: {2}{W}{W} Flying

though such a network tends to pull power from nearby devices

Set: Alpha Edition Type: Enchantment — Aura Rarity: Common Cost: {U}{U} Enchant creature

Set: EX: Unseen Forces Type: Grass Rarity: Holo Rare Retreat cost: Colorless

Set: Black & White: Black Star Promos Type: Water Rarity: Black Star Promo Retreat cost: Colorless

Voice of the Argoth forest

Set: Scars of Mirrodin Type: Legendary Artifact Rarity: Mythic Cost: {0} Metalcraft — {T}: Add one mana of any color