It need MageWizard's core to work!(www.planetminecraft.com/data-pack/magewizard-s-core/)

This datapack will be add powerful magic to your minecraft world. To obtain magic powers you need to kill a demon.
You need take a blaze rod from boss drop in your left hand.
Spells:
1 slot - Lightning
2 slot - Fireball
3 slot - Lightning spear
4 slot - Curse
5 slot - Shield
6 slot - Seven Suns of Cinnibus
7 slot - fly up
8 slot - hover
9 slot - fly down

How to summon a demon:
You need to build a structure like on the picture and drop a totem of undying on the beacon. Boss is very powerful, be careful!