Agatha of the Vile Cauldron has power 4 or greater.
({3} magic symbol) at most available.
Steps
Activate Cogwork Assembler by paying at most ({3} magic symbol) , creating a token copy of Mana Vault.
Activate the Mana Vault token by tapping it, adding ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) .
Repeat.
If Agatha of the Vile Cauldron has power 5 or greater, this combo nets infinite mana and you can then target any other artifact(s) using Cogwork Assembler.
Results
Infinite colorless mana.
Infinite copies of artifacts you control with haste.