I reckon using all of his mana was just an expression he used. Kind of like a strong man could use all of his strength to push open a heavy door, but it doesn't mean he would drop comatose afterwards and not move for a day.

I found it hilarious a couple of times during the episode when all the hurry to find Fran seemed to disappear in exchange for magic lectures and whatnot. In the meantime we saw poisoned Fran using her last bits of HP to try to resist the spider monster to live a few minutes longer. That was such an absurd dissonance in how the episode was constructed.

Quote Originally Posted by Buffalobiian View Post
Fran was lucky that the Trickster Spider was more interested in playing than killing. For someone that did such a great job fucking them over with various disarm and teleport spells, it didn't do a very good job when it counted.
On the contrary, I felt like the Trickster Spider was living up to its name. It was enjoying its various tricks and traps more than it would have enjoyed simply killing Fran and the two stooges.