Spar III
Since Michael was forced to use Foundation Break to keep up with the massive physical augmentation Ligno'vsh's Curse provided, he was losing lifeforce consistently. His lifeforce was nowhere close to being drained, and it would require a lot more than using Foundation Break at the first stage to suck him dry, but Michael didn't like where the fight was going.
He sustained more injuries in the last few minutes, and it was clear that the fight was going nowhere – at least, not in a good direction for him.
Michael used his control of the Curses and their, more or less forced, agreement to manifest several Seals. He didn't tap into the power of their Major Seals yet since he had no idea if the Wolf Curse and the World Serpent would gain an opening to infiltrate his mind, but Michael would switch to the Major Seals soon enough. He was just getting used to the new sensation the Seals exuded before going all out.