Some players will be slightly unhappy to hear that there is no straight-up archetypical magic user in AoC. There is no class that basically shoots fireballs while standing around like a glass window just waiting to be shattered into a million little pieces.
That doesn't mean certain classes couldn't be tweaked to play similarly to a more traditional MMO magic caster, but for better or worse you're going to have to use pets when you play a magic class in AoC. Well, unless you're planning on being a Herald of Xolti -- in that scenario you'll be using lots of demonic strength and magic.
Herald of Xotli
This is the class to play if you like three particular things: demonic magic, melee combat and badass transformations. To get all technical on you, the Herald of Xolti is a class capable of short range, high burst damage. This comes from their demonic, Xolti-powered transformations, which give them a large boost to their offensive and defensive capability.
As tempting as it may be to transform whenever an enemy appears, you've got to be careful. The reason being that there's a two minute cooldown on the Herald of Xolti's transformation ability. Typically, you really want to save it for the harder-to-crack classes and rely on your other powers if you get the jump on some of the health point-challenged classes.
What's especially nice about the HoX (Herald of Xolti) is that your feats allow you to alter the way you play. If you would rather focus on the melee combat more, while using spells less often -- you can. Or you can play it the other way around, participating in melee a bit while throwing around plenty of magic.
Both styles are equally satisfying, as I discovered. Ripping apart your enemies -- whether in demonic form or not -- while casting fiery brimstone magic was just as awesome as taking a few swings at a nearby magic caster before raining down all sorts of fire-based death on her previously-well-healed allies.
It's great that as a magic class, you can choose between higher damage or greater survivability. While you're certainly not a tank, it's nice -- as a mage -- to be able to handle some combat for a change.
Necromancer
When I first looked at the mage classes, I had to wonder: what's the big difference between the Necromancer and the Demonologist? Essentially, it's the type of magic they employ and the numbers and method in which they use their pets.
Spell-types come into play as well. The Necromancer makes use of two related magical types -- unholy and ice. I found that the ice magic was a great combination to use with the flayers as it tended to slow down my enemies with AoE (area of effect) spells, allowing my pets to rip things up a bit. Whereas focusing on unholy magics would increase the power of my zombie-style pets -- thus allowing them to hold their own in a melee bout.
Still, the classic problems of being a pet class did arise as I was playing in the PvP matches. That is; rogue type classes finding and quickly dispatching me. Of course this is all a part of the balance, so the thing to remember when playing a pet class is to avoid stealthy types. Feats are great for this, as they allow you to invest some points in being better at detecting hidden dangers such as Assassins or Barbarians.
A quick, odd note I'd like to mention is that of the randomly appearing ice creature that Necromancers seem to get. I only had it happen once or twice, but for some reason a giant ice monster would randomly show up as one of my pets. Whether or not this was a glitch or some kind of special random event is really unknown to me. All I can say is that it was definitely a "holy crap" moment whenever this guy made an appearance.
Demonologist
This was the last mage class I tried. Having already played the Necromancer, I was very curious to see how the Demonologist differed. The first big difference was obvious, you only get one pet at a time. In the case of my level 20 character, that meant I got a demon fairy -- which really looks like a succubus. When ordered to attack, my demon fairy would spout fireballs at my targeted enemy. This made managing my pet much easier, as she didn't have to close a gap to cause any damage like my Necromancer's pets.
Something that I thought was incredibly cool of Funcom is the fact that female Demonologists get a scantily-clad male demon fairy as opposed to the similarly-under-dressed female summon that male characters get.
The Demonologist seems to be about the closest thing you'll find to a straight up classic mage. While you do have a pet, your focus is really only on hurling out spells as fast as you can at single -- or multiple -- targets. Overall, it also seemed to be an easier class to play. So if you want to use magic, but don't want to have to micromanage your pets and your spells -- a Demonologist is perfect.
