Originally Posted by
Kitty
Ultimate Battle - Normal Overdrive randomly attacks 7 times, Raging Overdrive deals overall damage to all allies, and decreases their two-stage attack probability. (Special Skill can cut your DMG, so pretty much a DEF buff to Illuyanka)
Ragnarok Battle - Normal Overdrive randomly attacks 9 times. Raging Overdrive deals overall damage to all allies, and decreases their three-stage attack probability. (same special skill.)
As it states in the wiki, there is nothing that special to mention, so this is a pretty easy and straightforward advent battle, which is good.
The only thing to worry about is the special skill, which can be used at any time. It shouldn't be too much of a problem in experts/ultimates.