The armor was made of energy, so it didn't have to pay attention to any rules that bound physical beings. It couldn't feel pain, and it had no limits to the forms it could take. It created a multitude of arms that it turned into blades, which it used to fight back. It was willing to sacrifice a large portion of its body just to harm PRIDE a little.
Despite its bravery and its determination to fight to the death, the armor was losing the fight. This clone of PRIDE is far bigger than the previous one and also more experienced, so it is not giving Aeternus a chance at all.
It didn't care about resisting the corruption of its existence. Instead, it burned all of its energy in order to destroy Aeternus first before succumbing to corruption. PRIDE was burning so much energy that it turned into a bright star that threatened to burn his enemy to ashes.