The event will probably start in Jedi Day (May 4th). So beat the DARK side we should!

MAIN REWARDS:

DARK Eidolon Python
Deals DARK Damage to all enemies/Applies Barrier
DARK Attack +30%/DARK Characters' HP +15%

SSR Weapon "The Dragon Wand of Faros" (Staff)
Large Burst Damage
Skill 1 Abyss Vigoras - DARK Attack Up commensurate to remaining HP (+)
Skill 2 Dark Defender - DARK HP Up

SSR Weapon "Miasma Shooter" (Gun)
Large Burst Damage / Self Defense Up
Skill 1 Schwartz Defender - DARK HP Up(++)

SR Weapon "Regret Remains" (Axe)
Skill 1 Abyss Defender - DARK HP Up (+)

SR Weapon "Transviscerator" (Glaive)
Skill 1 Abyss Exceed - DARK Burst Damage Up (+)

Soul Points, Gacha Tickets, Magic Jewels, etc.

Why do the Devs hate DARK? The Japanese Wiki speculates that the SSR Gun will get a FLB in an Event Reprint