Ascalor's aura exploded inside the Prison of Light which made it shook a little bit. Ascalor did not expect that the Prison of Light will immediately get destroyed as he only poked it a little bit. Honestly, Ascalor would have been disappointed if the Prison of Light is destroyed with just a bit of poking as it would mean they got trapped in something weak.
Ascalor used half of his power this time and the Prison of Light started to tremble greatly. Normal people that would be inside such a shaking prison would have lost their mind or told the one making it shake to stop but the Daemos Elders are all calm. They know that this is just a reaction of a spell that is specifically made to trap them.