Best for: Players who want a step up from Moxfield's collection features without leaving the deck building ecosystem
They can also destroy any permanent (Angel of Despair), gain you life (Angel of Mercy, Lightkeeper of Emeria), destroy many creatures (Sunblast Angel), save creatures (Adarkar Valkyrie, Twilight Shepherd), reanimate (Reya Dawnbringer, Karmic Guide), keep alive indefinitely (Platinum Angel), shut down abilities (Linvala, Keeper of Silence), destroy all lands (Desolation Angel), give your creatures Indestructibility (Deathless Angel), and proactively prevent all combat damage (Blinding Angel)
The latter lets you cast a red or green creature spell for free, then you put three +1/+1 tokens on a target creature, and then you double a creature's power and toughness and give it trample until end of turn
These kinds of replacement effects don't affect the turn-based action of putting a single lore counter on a Saga at the start of your first main phase