I went with my head and to this day regret that decision
You can always play a card for its normal mana cost, in the top right Or if its in your hand, you can pay the adventure cost and send it away on an adventure
As long as you have enough non-land mana sources to produce two mana each loop, like artifact 'mana rocks' such as Sol Ring or mana dork creatures, you're golden
Since being released in March of the Machine: The Aftermath, Ob Nixilis, Captive Kingpin has flown under the radar somewhat
Though our very Commander is a damage amplifier, her effect is gleefully multiplied with each additional amplifier on the table, so we include cards like City on Fire, Furnace of Rath, Fiery Emancipation, Fire Servant, and Dictate of the Twin Gods for extra Scoville units