The mechanic represented the army of zombies that Nicol Bolas was creating from the Amonkheti people (which would play a critical role in the story of War of the Spark )
While shes out, any time an opponents creature dies, its exiled with a hit counter
In the past I have heard that this is an unfair advantage on turn one and that some Commander errata should be done to change the criteria on cards like this or Felidar Sovereign, but I am inclined to disagree on the basis that in a multiplayer game the advantage is pretty mitigated to the point where the Ascendant only makes you die slower and the Sovereign is good but often answered by someone at the table
Autobots Roll Out Liberty Prime, Recharged | Illustration by Pascal Quidault Beep-boop-beep-beep
If that were the rule, it'd let them move on to the card's second part with any number they wish, allowing them to play as many cards they just exiled without the energy cost
Its difficult to find balance with sweepers, as they have a way of either ending the game on their own or not mattering much at all, with games where they fall somewhere in-between being rarer than either extreme