Cogwork Assembler and Krark-Clan Ironworks on the battlefield.
({7} magic symbol) available.
Steps
Cast Myr Battlesphere.
When it ETBs, create 4 Myr tokens.
Sacrifice the tokens to Krark-Clan Ironworks, getting eight ({C} magic symbol) .
Use ({7} magic symbol) to activate Cogwork Assembler's ability, creating a toekn copy of Myr Battlesphere with haste and creating 4 more tokens on ETB.
Repeat for infinite Myr tokens, colorless mana and Myr Battlespheres with haste.