Use the Book of Souls to unlock new characters by summoning Souls. There is a whole cast of characters available that were made in collaboration with the band. Each character summon has a chance to be an Eddie.
You'll be able to obtain loads of characters, some of whom are ultra rare, so keep collecting those Souls!
With 5 different character classes, each with unique play styles, there are virtually unlimited opportunities to create powerful teams with unique synergies.