A: Invisibility is a little overpowered...situationally.
Generally speaking, enemies can see and react through Invisibility to some degree, in many situations.
But then there's times where, due to lack of Invis sight, etc., an entire large room full of enemies doesn't and slowly gets cut to pieces. This is hilarious, but sort of too much.
Idea for this: Have a (low) baseline for everyone in the game to see through Invisibility(but not stealth! Stealth doesn't need a nerf, it's in good shape.). Say, 5% chance every turn. Even once enemies know you're there, Invisibility is still very useful, but enemies never figuring you're there is ridiculous. Thematic, but overpowered when it happens.
Passing out a little more see invis(Maybe some more to demons?) wouldn't hurt, but that's the big thing.
Actually, you could probably solve the issue just by passing out Piercing Sight to, say, thief type enemies and mage type enemies. That might be even better, thinking on.
B: Negative regens get boosted by resting.
This is kinda frustrating-it was very often better to not rest with Invis on, than it was to rest with Invis on, since my negative regeneration would increase to ridiculous levels that autocasting Manasurge couldn't handle.
Idea for this: Don't let resting boost negative regens. Please. It was just annoying.
C: Ambuscade is sorta silly.
Ignoring some recently reported bugs about changing skills while under the effect(Which I easily avoided, thankfully), Ambuscade still is a little abusable with controlled teleport. It's quite possible to simply have your Ambuscade teleport across a dungeon, slowly killing everything in it. Goofy and overly good if you're really boring.
Idea for this: Have an Ambuscade evaporate/die/whatever if it goes beyond (10+talentlevel*5) squares away from the host. This'd at least make it more of a short range abuse than a long range one-more along the lines of a normal summon, instead of a massive range one.
D: Shadow Veil does some weird things.
D1: Shadow Veil only functions once per "global" turn, as in the rate that status degenerate etc. at. If you have more than 100% speed, as such, turns taken under Shadow Veil will be fully controlled. This may be a good thing, though...it's quite questionable without that, for normal use(as opposed to an Ambuscade casting it), and it's hard to get up enough speed to stay reliably in control without burning resources or something similar.
D2: Shadow Veil, when used by an Ambuscade, seems to not take up remaining summoning time turns for Shadow Veil attacks. This is a little bit silly and leads to Ambuscades being able to last 15-20 turns. This is somewhat more abusable, though there's still somewhat of a question if it's a bad thing.
D3: Shadow Veil, when used and then Ambuscade cast, will cause your unconscious body to run around Shadow Veil attacking people, if they are in range, as well as your Ambuscade. This is hilarious, and while it's extremely damaging, it's also extremely risky since you have to stay entirely out of control of your body-aka the part that game overs you when you die. It's probably fine.
Solution: Heck if I know. I don't even know if any of these needs a fix-it may all be intentional. It's pretty funny though, and worth commenting on.
E: For some strange reason, world map enemy sets can reliably see through Invis.
Solution: Heck if I know. I didn't think they had any see invis. It's funny to be chased unerringly by a squad of enemies and then have none of them know where you are when they catch up to you.
F: You can't always see through your own invis. And, at least on very low graphical settings, your tile just disappears when this happens. So, it can be hard to figure out where you are.
Solution: Make it possible to see through your own invis or make a no-shaders graphical effect to note where you are, I guess.
Overall, though, it was really fun. Shadowblade starts out hard and has a really, really strong later game, and Tricks of the Trade worked out very well. Fun stuff.