In general, when looking at power level, I considered the overall game plan, the synergy of the 99 with that game plan, things like interaction, ramp, mana base and card draw, the commander, and the power of the remaining stand-alone cards
We already have black ramp with Cabal Stronghold that can fire out some of the bigger demons on earlier turns, but we need something that plays in the early game
Arbor Elf You need a reason to play Arbor Elf over other 1-mana dorks like Llanowar Elves and Birds of Paradise
Just like Neo Upper Energy, Legacy Energy can provide 1 of any type of Energy at a time
Main Collectable Card Games Magic: The Gathering Radiation (Token) Radiation (Token) Card Text: At the beginning of your precombat main phase, if you have any rad counters, mill that many cards