Legion had used 45% of the energy cost of the attack to block the attack. In return for blocking the attack, they reflected it back to their enemy and gained 50% of the attack in the form of life energy.
If they were injured in any way, that life energy would have come in handy. The attack that was supposed to kill them would have saved them. This was how disgustingly unkillable an undying godclad was.
But they were not injured, so they didn't need the extra life energy to heal. However, they had another divine ability from their other pathways that could use the extra life energy.
As for their other divine abilities from the pathway of undying, they didn't activate because they didn't need to. The three divine abilities that did were more than enough to resist the attack and counterattack successfully.
Not only did that rule refuse to work on Legion, it also backfired. The legendary noble had wasted this spiritual energy to stop them.
