The repeated Heat Shimmer mode is also very expensive, and its only good with specific creatures with enters abilities or huge threats
Ideally, you'll be able to build up speed before casting The Speed Demon, but it works just fine if it starts your engine
By shockingly affordable, I mean Im pleasantly surprised at how cheaply you can pick up copies of Boromir now, despite the fact that he easily slots into literally any white deck thats playing even a minimal number of creatures
While Necrodominance is on the battlefield under your control, abilities that trigger whenever a permanent you own is put into your graveyard from the battlefield (for example, "When this creature dies") won't trigger because cards and tokens are never put into your graveyard
For example, Sakura-Tribe Elder's activated ability lets you put an Omnipresent Impostor onto the battlefield tapped, while Goblin Engineer's enters ability lets you put an Omnipresent Impostor into your graveyard
That means, assuming youre not doing anything more absurd than simply casting it, that you can draw seven cards, basically for free, every single turn with no issues