I generally run a 50% corrupted build with 19/20 in corrupted authority for that extra Nergal fly time which I love, I find it helps with scouting the map so much, particularly when you’re trying to find players hidden in ratholes sunken within cliffs that you generally wouldn’t see from the ground up.
Summon Corpse: Currently with the glitch you can perform to summon your corpse basically for free is great! Even when they ultimately patch it out it’s still a very useful spell, they definitely need to keep this one.
Mass cull: Also a great spell that I use ALL the time, it allows me to mass farm stone/wood/crystal/ironstone in no time at all.
Transportory Spell: So good! Having a means to get from here to there in conjunction with the maprooms travel options is so good!
Elixir of Rebirth: Another great option to have, being able to give your thralls another chance at better stats, can’t complain with this one.
Conceal Corruption: It does what it does and I love it, I like to play with sorcery but I don’t want to play with a shriveled up husk of an avatar.
Invisibility: Also a great spell that I often use to tail enemy players where if I’m lucky will take me directly to whatever hidey hole they are working out of or at least let me tail them through whatever doors they open at their base so I can have a good look around.
Ice bridge: It’s allowed me to easily access and check out enemy bases that are surrounded by crenelations or spiked walls or just get over annoying gaps when I don’t have the stamina to climb.
Slow fall: It has had its uses here and there but I don’t use it THAT often, I wouldn’t get rid of it though.
Other than that, I’ve never really had any great reason to use any other spells, but in saying that though:
The Darkness spell: I could see it being useful if being raided and you want to add some difficulty to their raid or if you’re being tailed by other players but I’ve honesty never used it.
Lightning Storm: I wish the lightning storm spell would get buffed, I know it was way too powerful when sorcery was first introduced and could open access to bases way too easily, but now I feel like for what it costs it’s just way to weak.
Firewall: I can’t really see myself using this effectively in any situation other than MAYBE closing a small/tight gap when you’re being chased by an enemy, but at the same time because there are gaps in the walls when you summon it, it’s not worth the risk to stop and summon it, better to just keep running.
Summon Dead: I’ve never used this one, since the zombies will also attack your own guarding thralls and my own guarding thralls will attack them too, it may potentially offer an advantage to any invading enemy if my thralls are too busy attacking zombies.
Wisps: I’ve used this every now and then when I’ve forgotten to bring a torch, it’s kinda handy in a pinch but ultimately not that great, I could see it being useful if you’re being raided in the dark and you want to maintain a light on an enemy player for your clan to keep tabs on but first you’ll need to accurately land the spell.
The armor/mount/weapon spells: Never used them, can’t comment on their usefulness.
Reveal corruption: Never saw any use in this one.
Mirror Mask: I can kinda see some use out of this maybe, creating a distraction so you can get in and do what you need to do without being attacked, but as far as I can tell the replicants don’t last that long…
Raise Dead: I’ve never used this one, I know when you raise dead the thralls you bring back are insta lvl 20’s which is kinda cool but with the current glitch where you can insta lvl regular thralls anyway, it seems a bit redundant.
I feel like a bunch of these spells could be replaced with something more substantial/useful, some examples that comes to mind is resistance to heat/cold effects, perhaps a temporary resistance to gas, nightvision, maybe slowfall could also give the double-jump perk, maybe temporary increased HP/Stamina, maybe instead of detect resources you can detect player built structures instead?