So, if the 10 souls that you can earn from the challenges don't get you either of the two event-exclusive characters, you have to buy 40 souls to guarantee Domino (3600 Ironite) then another 25 to guarantee the new Eddie (additional 2500 ironite). If you have such bad luck that none of the souls result in the two event characters.Each Rock On Soul summoned will also grant the following bonus rewards:
10 Scream for Me Eddie Soul Fragments
10 Domino, Woman in Uniform Soul Fragments (Assassin)
750 Scream for Me Eddie Soul Fragments guarantees one 5★ Sentinel Scream for Me Eddie!
Collecting 500 Domino, Woman in Uniform Soul Fragments guarantees one 5★ Magus Domino, Woman in Uniform
10 Souls that can be earned from challenges over the course of the event.
And no doubt several players will get multiples of the event characters, some from the 10 souls they get from the challenges.
I'd prefer that events were more like... when there's an Eddie and another character released, then it'd be more like...
complete all challenges, gets you enough thingies to be guaranteed the character, but you'd have to buy souls to be guaranteed the Eddie.
So in this instance, 10 event souls from challenges = enough to guarantee Domino, but not to guarantee Eddie.
So that if you do complete all the challenges you do guarantee the minor character.
Otherwise, why go through the pain of connection errors to complete the challenges ?