Eisen stood in front of the structure that created yin and yang materials from yin and yang masses, trying to figure out what he could possibly do to create more high-tier materials. Or rather, to create as many materials as possible in as little a time as possible.
What Eisen could do is let himself be taken over by the curses and blessings in an environment where the 'Wild' version of him couldn't have a chance to escape. That 'wild' version was supposed to still be a thing even after Eisen revived, that's exactly what Eisen was going for. It was an actual 'Being of Yin' or a 'Being of Yang', instead of just a mass. If Eisen could kill those beings and create the compound from the corpses, or create a direct 'Being of Yin and Yang'. There was sure to be some sort of benefit to doing that and 'offering' that instead of just regular masses.