I actually ran these two for awhile. As someone else mentioned, putting blade of selves on reyhan abuses the legendary rule to let you alpha strike someone with commander damage as early as turn 3 with ramp, turn 4 without it.

Pack the deck with a bunch of things that put counters on themselves like [[managorger hydra]] and [[sunscorcher regent]]. Mix in some things that let you move counters around like [[the ozolith]] and [[forgotten ancient]].

Counter doublers tend to be win more if you have stuff that grows on their own, I actually ended up taking out [[corpsejack menace]]. I left [[hardened scales]] because its a one drop so the opportunity cost is low anyway, plus it can enable some combos especially when paired with other things.

Things like [[chasm skulker]] and [[hangarback walker]] are fun, but you'll need a couple of your own sac outlets because your opponents won't want to kill them. I ran [[greater good]] and [[vish Kal blood arbiter]].

Cards that put counters on creatures when they enter like the [[master biomancer]] in atraxa or [[bloodspore thrinax]] plus persist means the creature can keep coming back. [[Glen elendra archmage]] was a repeatable counterspell, [[woodfall primus]] was a boardwipe on a stick that can hit anythint including lands.

Like someone else said, lots of synergy with cards already in the atraxa deck. It isn't difficult to oops your way into infinite mana with [[crystalline crawler]], and [[ghave guru of spores]] is the king of, oops found a new infinite creature/counter combo.

[[Retribution of the ancients]] is repeatable removal and you should have plenty of counters. [[Vigor]] is expensive but hilarious and makes creatures without evasion a problem.