There are many powerful Demons in Magic (just ask Liliana), and having access to them at any time is a potent ability
Check out the core deck list, key combos, how to play & counter as well as alternative options
There are 3 types of cards that can go in a deck: Monsters, Spells, and Traps
These cards are all reprints from earlier sets, and each set that uses set boosters or play boosters has some cards on The List
In competitive play, there are generally stronger Rank 9 options such as **True King of All Calamities** (historically far more oppressive, though forbidden), **Number 90: Galaxy-Eyes Photon Lord** (for Galaxy decks needing negation), or **Divine Arsenal AA-ZEUS** (as a superior board wipe follow-up to Xyz plays)