Should add it to upcoming events soon:

Break of the Nutaku Aigis (Break Event)

A break event is an event where nothing actually happens. The units from the event are available at random in the summons.
Event unit:
-Premium Summon randomness
Completition Reward:
-Story mode silvers
Spotlight Units:
-Whatever tickles the dev's funny bone.
Farmable silver units:
-Premium and Basic Summon randomness
Farmable spirits:
-Silver to rainbow
Farmable Crystals and Armours:
-Dailies