A few days ago I started a Redguard assassin/stealth build, it may not make much sense but well it's my choice. I tried Illusion cause some people suggested it and said it was that good. I raised Illusion to like 78 in and hour or so with muffle casting+wait 1 hour, but since then I haven't really seen any use for the skill... Not only that but also it's hard to use. I admit I only have Novice and Apprentice spells and that may be my problem but if not.. Can anyone explain me how to use it? I have all perks in except adept, expert, master and Master of the Mind.

Any tips? Otherwise I will be using Conjuration or something. Not that I really need it but just for the fun of it. That or I'll full perk my Smithing tree to get some ebony or dragon swords..

Aside from the obvious invisibility and muffle spells, the calm and frenzy spells are very useful for a thief/assassin as well as any mage. If you get caught pickpocketing or breaking into someones house and they turn hostile, throw a calm spell at them, then retreat the other way.

If a group of bandits are storming at you, toss a fury/frenzy spell at them and watch them attack each other.

Illusion is different in that its a more defensive school focusign on the mind and manipulation. But you need all the perks for it to be most effective. It's all or nothing with this skill.

Lots of different strategies here. For stealth, you want Invisibility (and expert perk) and quiet casting if you if you use other magic. Cast Muffle, then Invisibility and you can go anywhere and set up the perfect sneak attack.

For control, you need the Master of the mind perk so it will work on undead. Then frenzy your enemies or calm them. If you have dual cast and all the perks, it will work at all levels.

For a stealth character muffle and invisibility(thats an expert spell).

Frenzy will get your enemies to kill each other doing your work for you.

If you get caught out of stealth sometime a good calm spell can save your life.

Illusion is one of the most powerfull skills you can learn.

And yet the most underrated (magic) skill in my opinion.