Barbflare Gremlin

First strike, haste
Whenever a player taps a land for mana, if Barbflare Gremlin is tapped, that player adds one mana of any type that land produced. Then that land deals 1 damage to that player.

Mana Flare

Whenever a player taps a land for mana, that player adds one mana of any type that land produced.

Belbe, Corrupted Observer

At the beginning of each postcombat main phase, the active player adds {C}{C} for each of your opponents who lost life this turn. (Damage causes loss of life.)

Scryb Ranger

Flash
Flying, protection from blue
Return a Forest you control to its owner's hand: Untap target creature. Activate only once each turn.

Citadel of Pain

At the beginning of each player's end step, Citadel of Pain deals X damage to that player, where X is the number of untapped lands they control.

Power Surge

At the beginning of each player's upkeep, Power Surge deals X damage to that player, where X is the number of untapped lands they controlled at the beginning of this turn.

Forest

Quirion Ranger

Return a Forest you control to its owner's hand: Untap target creature. Activate only once each turn.

Seeker of Skybreak

Ornamental Courage

Untap target creature. It gets +1/+3 until end of turn.

Yurlok of Scorch Thrash

Vigilance
A player losing unspent mana causes that player to lose that much life.
{1}, {T}: Each player adds {B}{R}{G}.

Zhur-Taa Ancient

Spectral Searchlight

{T}: Choose a player. That player adds one mana of any color they choose.

Marvin, Murderous Mimic

Marvin, Murderous Mimic has all activated abilities of creatures you control that don't have the same name as this creature.

Raggadragga, Goreguts Boss

Each creature you control with a mana ability gets +2/+2.
Whenever a creature you control with a mana ability attacks, untap it.
Whenever you cast a spell, if at least seven mana was spent to cast it, untap target creature. It gets +7/+7 and gains trample until end of turn.

Stoneshaker Shaman

At the beginning of each player's end step, that player sacrifices an untapped land of their choice.

Victory Chimes

Untap Victory Chimes during each other player's untap step.
{T}: A player of your choice adds {C}.

Zhur-Taa Druid

{T}: Add {G}.
Whenever you tap Zhur-Taa Druid for mana, it deals 1 damage to each opponent.