There are at least four permanents of any color on the battlefield.
Breath of Fury attached to any creature you control except Rith.
An opponent cannot block creatures you control.
You control at least one Mountain.
({2} magic symbol) ({G} magic symbol) available.
Steps
Deal combat damage using Rith and the creature with Breath of Fury attached, triggering Rith and Breath of Fury.
Resolve the Rith trigger, causing you to pay ({2} magic symbol) ({G} magic symbol) to create at least four 1/1 Saproling creature tokens.
Resolve the Breath of Fury trigger, causing you to sacrifice the creature it is attached to, then attach Breath of Fury to a Saproling token, then causing you to untap all creatures you control and to get an additional combat phase after this one.
Move to your next combat phase, and deal combat damage using Rith and the creature with Breath of Fury attached, triggering Rith and Breath of Fury.
Holding priority, activate Phyrexian Altar three times by sacrificing three Saprolings, adding ({2} magic symbol) ({G} magic symbol) .