Phillip is trying to consider his options- he can get his mana back, but the natural exchange is that he'll be doing less damage, give the soliders surrounding them both more time to hurt them. Transcending his form is the last option on the table. He can do it, he will do it if there's no other way to make sure Gustavain gets out of this, but he also genuinely has no idea what it'll do to him, if the part of him that is even a little bit mortal will survive the process.

The bard falling distracts him, whipping around on instinct to try and help him, blasting the solider approaching him out of the way. Unfortunately another caster takes the opportunity to fire back, catching him off guard and making him stumble, crouched on one knee. His breathing is sharp, and he realizes he may not have a choice--

Gustavain will be able to sense it, the darkness of the Ascians beginning to swell; if he wants to prevent it from happening, he doesn't have much time.