While Sram, Senior Edificer is also good draw, its only off of cast, and so should always be second choice to Puresteel
This human cleric generally works best on your turn so you have the best chance of using that mana, though black has plenty of 2-mana removal spells to fire off at instant speed
Simply having a large mana dork that replaces itself is pretty good, but vigilance does a lot of work here, allowing the Adventurer to fight over and defend the initiative
Sidar Kondo of Jamuraa makes a great pairing as he makes your bird army tricky to block
But despite the power here it's not my top option from the set
We arent given percentages, so Im running with the idea that all are equal and with 163 options, over two slots, youve got a 1/81.5 of getting the specific EA you want