You have at least two opponents who each control at least one artifact.
({1} magic symbol) plus enough mana to pay for commander tax, if applicable available.
Steps
Cast Journey On either from your hand or from the command zone by paying ({1} magic symbol) and commander tax, if applicable, creating at least three Map artifact tokens and exiling Journey On with the ability to cast it from exile.
Activate Krark-Clan Ironworks by sacrificing three Maps, adding six ({C} magic symbol) .
Cast Kellan from exile by paying ({2} magic symbol) .
Activate Temur Sabertooth by paying ({2} magic symbol) , returning Kellan from the battlefield to your hand.
Repeat.
Once you have infinite mana, you may forego sacrificing the Maps, and you may use the Maps to put infinite +1/+1 counters on creatures you control.