Umbral Mantle attached to Yurlok of Scorch Thrash.
Yurlok of Scorch Thrash does not have summoning sickness.
({1} magic symbol) available.
Steps
Activate Yurlok of Scorch Thrash by paying ({1} magic symbol) and tapping it, causing each player to add ({B} magic symbol) ({R} magic symbol) ({G} magic symbol) .
Activate Yurlok of Scorch Thrash by paying ({1} magic symbol) and untapping it, causing itself to get +2/+2 until end of turn.
Repeat an arbitrarily large amount of times.
It is strongly recommended to empty your mana pool using a mana sink before proceeding.
Move to your next step or phase, causing each player to lose life equal to the amount of unspent mana in their mana pool.
Each player whose mana pool contained an amount of mana equal to or greater than their life total loses the game due to having 0 or less life, which causes a draw if every player lost the game.