Prossh, Skyraider of Kher | Signpost Scarecrow | Ashnod's Altar

Cards

Cast
Prossh, creating 6 kobold tokens.Sacrifice6 tokens to Altar to produce ({12} magic symbol) .
Use ({6} magic symbol) to produce ({B} magic symbol) ({R} magic symbol) ({G} magic symbol) with Scarecrow.Sacrifice
Prossh to Altar to put him back into the command zone.
(also producing ({2} magic symbol) ).
Floating ({8} magic symbol) ({B} magic symbol) ({R} magic symbol) ({G} magic symbol) , recast
Prossh for ({5} magic symbol) ({B} magic symbol) ({R} magic symbol) ({G} magic symbol) , producing 8 tokens.Sacrifice them all to Altar producing ({20} magic symbol) , filter again, and repeat.