Mordan and Viktus are the “second” encounter in Infinity Gate. Although they can be summoned as the first boss, Breaker X-1 is easier in my opinion.
They are the Life and Death brothers and they sit on separate platforms, between which the raid will have to jump across.
There aren’t a lot of mechanics to deal with in this fight, the key element is getting the time when to switch platforms right.
I find the fight fun, I like the fact that sometimes things go wrong and the fight turns hectic, the only thing I hate is wiping on these bosses ! Ressing and rebuffing is a pain !
Good luck !