After certain stages in the Ninja Tower players will be given an opportunity to choose an Oni Blessing. Blessings are buffs that will remain active on all your Heroes in the Ninja Tower Event. Like Oni Curses, Blessings cannot be removed or dispelled and will remain active for the entirety of the Event.
The Oni Blessings a player currently has active can be seen before entering battle or by tapping on the star on the left side of the screen during Ninja Tower Battles. It is possible to have multiple blessings active at one time.