@matuto : I'm aware the frame rate is lower, specially in the garden part of the forest (first part of the game). Unfortunately, I haven't found a way to improve the situation without a huge overhaul of the mod. About the crash to desktop, can you post the log ? Water and air spells shouldn't crash the game, they haven't been modified. Open simple lock is an a new spell, but I will need more info (what did you cast it on, crash/error message, etc.)
@hansbleed : About the land of the dead
Do NOT use any form of light source, like torch, light spell, etc.. This summon the undead ! The skull and the Scythe are in their respective mauselum and crypt (Tower of lost Souls). I strongly suggest to get the Nexus Key (optional puzzle in the Academy Tower)
Stewart of Death and Insanity
This guy has a shield, so you need to damage it first before you can drop his "life" bar. If you got the searing light spell and the soul weapon (at their top level), it's a huge help. Do not cast regular spell on him, he will absorb them.
Extra tip :
If you are having a hard time, did you defeat the optional bosses (2 bosses in the mine, one at the very top of the Academy tower, they drop Souls Weapon, the more you use them, the stronger they get.