Cure, Attribute, Weapon, Pet, and Seat of Transcendence. They were the five Major Treasures that appeared in Sumatra Chronicles. And the extent of Renduldu's arrangements lasted only until the end of the Fourth Major Disaster.
It would mean the Mammoth Clan's loss if Brangara obtains the Seat of Transcendence. It didn't matter if he killed all the reincarnates. When that happened, Resha would be able to grab the Major Treasures and Minor Treasures from the corpses of the reincarnates.
He was the sole individual capable of fusing with them all. Hence, when Brangara obtains the Seat of Transcendence, Resha could take the chance to flee. Anyway, his experience of facing four Major Disasters, against Brangara in every single Major Disaster would translate to enough experience necessary to fill the Red Mystic Path.