Damian's plan was simple but it was his best bet a surviving and keeping the beast core that he was unwilling to hand over.
He planned to use one of his fast and powerful skills, using the Maxwell Fire Soul Spirit that he still had activated, then quickly switch his Changeable Energy into Shadow Energy, giving him a boost of speed and maybe he might be able to get away.
As long he could surprise them with the attack and they are dazed by it for a moment, Damian should be able to get away and although they would catch him shortly after, since he was injured and fatigued, if he headed deeper into the Beast Woods, they might be afraid to follow him.
Although it was reckless and dangerous to head deeper into the Beast Woods, especially in his current state, there was a chance of survival if he could find a place to recover, unlike if he attempted to face all 5 of them.