Activate Door to Nothingness by paying {W}{W}{U}{U}{B}{B}{R}{R}{G}{G} and tapping it, targeting yourself.
Holding priority, cast Radiant Performer by paying {3}{R}{R}.
Radiant Performer enters the battlefield, copying Door to Nothingness' ability for each opponent.
Resolve each copy of Door to Nothingness' ability, causing each opponent to lose the game.

Each opponent loses the game

Radiant Performer

Door to Nothingness

Activate Door to Nothingness by paying {W}{W}{U}{U}{B}{B}{R}{R}{G}{G}, tapping and sacrificing it, targeting an opponent.
Ashnod the Uncaring triggers twice.
Resolve the first Ashnod the Uncaring trigger, copying the Door to Nothingness ability, targeting an opponent.
Resolve the Door to Nothingness ability created in step 3, causing the targeted opponent to lose the game.
Resolve the second Ashnod the Uncaring trigger, copying the Door to Nothingness ability, targeting an opponent.
Resolve the Door to Nothingness ability created in step 5, causing the targeted opponent to lose the game.
Resolve the Door to Nothingness ability in step 1, causing the targeted opponent to lose the game.

Combos with "Door to Nothingness"