So I am going for a new class that is a defensive stealthy mage hybrid. I know most of what I plan to do for this character but I am still debating on a few points. What I am debating on is whether or not focus on Illusion, I dont really plan to be a hardcoe assassin type so I am not trying to maximize pure stealth with invisibility and/or muffle. I am more interested in the illusions skills of pacify, fear, etc., so what I am curious about is whether or not those spells are actually useful. I have heard from friends that Illusion just isnt very useful as a core magic school at upper echelon levels and that going destruction, conjuration, or alteration is better. So for all you mages/rogues out there who know, I would appreciate your insight on this.

(ideally I want to use alteration and not really use destruction or conjuration much, my damage output will be with my one handed sword, I just dont know if illusion should be a primary focus in my character)

Illusion is probably the most overpowered of the magic schools, even excluding invisibility.

Just being able to frenzy an entire group of monsters into killing themselves or using calm to essentially reset combat is pretty powerful.

I have played an Illusion-based 100 HP character on Master, and actually thought it was almost stupidly OP. Once you got the hang of the play style you shouldn't have trouble being successful.

Quiet movement is very helpful even if you aren't an assassin. My Mage, being unarmoured, needed stealth to help me take a few guys out at range, before all heck broke loose. Needing to keep bad guys at bay I focused on conjuration and destruction. the impact perk (destruction school) is critical for that. Ice spike is your friend. Dual-wielded will stop Giants and Deathlords in their tracks.

I have heard similar complaints about illusion in that it doesn't work very well (or at all) against higher level dudes. In addition I find it difficult to know what level some bad guy is and whether or not its worth to hit him with an illusion spell.

Dragons are the only opponents immune (once you get Master of the mind, anyway), so with the right perks and spell choice (you may have to dual cast) the effect will stick.

It is really more of an annoyance than anything and you will eventually just know what each enemy type requires. The only other thing you could consider a drawback is that there are so many enticing perks in the tree.

Yeah, I worry about spreading my perks thin. I am using one handed, light armor, smithing, alteration, and sneak

I don't know if I'd call Illusion overpowered because you need to get to a relatively high level before you can really count on it as a main weapon/feature. For example, Calm may or may not work on some opponents when you're at level 30, but Pacify stops groups of bad guys in their tracks when your skill is at 90. Even bosses.

Keep in mind, you can dual cast illusion spells to double the level of creatures it can effect, inclusive of such perks as animage or kindred mage.

So, if you have the illusion dual casting perk, available at illusion skill 20, you could be level 2 and be able to calm opponents that are 15 levels higher than you with the lowest level calm spell.

That's not really realistic... you would have to be level 3 to have enough perks to buy dual casting, and you would have nowhere near enough mana to even utilize it.

However, Hypnotic Gaze makes Calm reliable against most opponents through the mid-teens. Illusion is basically as powerful as you make it.