here is my build for my Embermage:
http://torchlight2armory.com/skill-calc ? e4bLqaWnBV
(hope the link works)
It`s highly effective and very easy to play, you dont need any kind of special equip, you can try it out with a respec potion instantly.
It is also very flexible for customization, because it needs only a few key skills to work.
Skills you need:
It is the main source of damage for this build
All three skills are essential to boost the damage output of Infernal Collapse
This is your main crowd control ability and very important for the effectiveness of Infernal Collapse
This skill serves two important roles: On the one hand, it grants you additional crowd control because it slows down enemys (and later stuns for 2 seconds), even bosses, on the other hand, its an important source for mana and health, you dont need even charge for this build.
The rest of the skill points is up to you, you can either add additional damage output or some other crowd control features, or some passive skills.
-Astral Ally (he doesn?t do a lot of damage, but I will drop him down the day he doesn?t save my ass anymore?)
-Frozen Fate (additional crowd control and easier use of Infernal Collapse)
-Immolation Aura (additional damage and damage absorption)
-Just do whatever you want
The Path of Total Destruction:
-Just use Death?s Bounty and Ice Prison on single targets or groups of enemys. You can use Ice Prison to trap one single enemy, to block paths, to block the direkt way to your mage (essential on boss fights), to block projectiles on their way to you etc. etc. The combination of this two skills is the total destruction for every formation of enemys, for every attempt to get quickly to your mage and so on. It also makes it easy to deploy your infernal collapse ? skill, there is no problem with the delay of the spell, because enemys are not able to get out of range in time.
-Before you start nuking the shit out of your enemys, just deploy Firestorm and turn on Elemental Boon.
Attributes: Just put everything in Focus and Vitality. If you like to be a glass cannon, just nearly everything into focus, I recommend a good pack of Vitality, it synergizes very will with death?s bounty.
Just try it out and have fun to play!
PS: I recommend a one-handed staff and the best shild you can use, because you dont need your staff?.