Quick rundown.
As soon as you step through the gate, sprint left to avoid first beam.
Summon your spirit and replenish mana.
Run towards Astel from the left side, while still dodging his follow-up attack.
Use Rotten Breath when your summon has agro.
Avoid crashing comets by strafing left with Shield on Guard, then roll when you see them flying towards you, should typically be 2 or 3 times.
