It takes a long time to get the hang of playing Scroll Rack properly even in a normal deck
Bloodghast: Sacrificing creatures for gain is one of blacks best tricks in Commander, and Bloodghast is a very strong piece of sac fodder, requiring no mana and potentially entering the battlefield multiple times per turn, thanks to Terramorphic Expanse/Evolving Wilds/Panoramas/fetches
Even if youre not winning via a flashy combo, its great value to cast some spells, hit with Storm, and cast a Lightning Bolt or a Preordain
But with counter doublers like Lae'zel, Vlaakith's Champion and proliferate triggers, youll have no trouble turning your 2-drop commander into a board wipe that threatens lethal damage with just one attack
The versatility of being able to pick and choose which effects to prolong and for how long makes Grand Marshal Macie an interesting and powerful commander