({3} magic symbol) ({W} magic symbol) ({U} magic symbol) ({B} magic symbol) , plus additional mana dependent on how many creatures have died this turn and commander tax available.
Steps
Cast
Nevinyrral by paying ({3} magic symbol) ({W} magic symbol) ({U} magic symbol) ({B} magic symbol) plus commander tax.
Nevinyrral enters the battlefield.
In response, activate
Phyrexian Altar by sacrificing
Nevinyrral, adding ({1} magic symbol) .
Decline to pay for
Nevinyrral's leave the battlefield trigger.
Resolve
Nevinyrral's ETB trigger, creating a tapped 2/2 Zombie creature token for each creature that died this turn.
Activate
Phyrexian Altar by sacrificing all Zombie tokens, adding ({1} magic symbol) for each.
Repeat.
Results
Infinite colored mana.
Infinite death triggers.
Infinite ETB.
Infinite LTB.
Infinite sacrifice triggers.
Infinite tapped creature tokens.
Metadata
In 544 decks according to EDHREC.
Bracket Tag
This combo has been estimated to be Ruthless (Bracket 4+).