The difference between these cards and Game Changers is that Game Changers, while strong, are labeled Game Changers with Commander's social setting in mind
I saw it while it was up and while some looked good many were oversaturated, had wrong holo patterns, and had inconsistencies that are known with proxys like their borders
Activate only as a sorcery and only if you've cast three or more instant and/or sorcery spells this turn
Combo cards are scattered all over blues history, as well as disruption to make sure your opponents cant combo
Midnight Reaper + Friends There are actually a ton of these little card advantage dudes, including Midnight Reaper, Liliana's Standard Bearer, Headless Rider, Archghoul of Thraben, and I could probably go on but Ive got some dead ones nipping at my heels
You could target a single creature card with Call of the Death-Dweller