Incursion combat mage

Combat Mage

Stats:
STR 16
DEX 14
CON 14
INT 15
WIS 14
CHA 8
LUC 14

STR helps, but Decastave and quarterstaves in general don't get damage bonuses from strength, so 16 is fine. 14 LUC because LUC is good and Mage Armor is more effective with higher LUC, and the rest is self-explanatory.

Race:
Human

Feats:
Power Attack
Cleave
Mounted Combat
Ride-By Attack
Spirited Charge
Great Cleave
Supreme Cleave
Expertise

At level 5 and 10, you get a free magic-related feat. Just pick whatever you like from the small list it gives you.

Normally, I would recommend Knock Prone, but for some reason, it just doesn't seem to work with the Decastave.

Skills:
Pretty much the standard Mage stuff, but put points into Ride, too.

If you don't put Ride as one of your 2 racial skills, you can still put 1 rank into Ride per level, but not having Ride as a class skill means that while you can cast Mount and get mounted on a horse that way, if you dismount from your horse, get knocked off of your horse, or are otherwise separated from your horse, you cannot manually mount that horse again, and would instead have to cast Mount again to be mounted on a new horse. Mount is a persistant spell, so it eats up "permanent" Mana, so this would be quite inconvenient. You could opt to spend a feat to get Ride as a class skill, but you would have to sacrifice one of the above feats to do so.

School:
Thaumaturgy. This ensures you start with the right spellbooks, so you know False Life right off the bat, and you can learn Decastave promptly at level 3. (I've found that the book that contains the spell Decastave, Ars Bellicus, is slightly rare.) You also get extra HP per level as a Thaumaturgist. The only downside is that casting spells your school focus opposes costs more Mana and has a chance to drain your fatigue, and Decastave is one of those spells, but the pros outweigh the cons in this build.

Description:
The combat Mage is a great build. All the buffs you'll be using make you end up with better survivability than even heavy armor Warriors, you can certainly dish out the damage, and you have most of the versatility of a normal Mage. Be sure to equip your quarterstaff, as you start out wielding daggers.

The main aspect of this build is the spell Decastave. It conjures a quarterstaff made of force. The Decastave has a really high crit rate (17-20, whereas the best crit rate a mundane weapon can boast is 18-20), does more damage on a crit than a normal quarterstave, has faster attack speed than regular quarterstaves, and since it's a force construct and not a material weapon, it cannot be broken; this is why the build centers upon the Ride skill and the Mount spell, because the Decastave isn't subject to the chance of breaking while charging, unlike material weapons, so you can charge constantly to get melee bonuses without risking breaking your weapon.

Pretty much just grab whatever persistent buff spells look good, but make sure to get Mount, and especially focus on buffs that help in combat (and ignore the dagger-oriented spells, as we're going with the quarterstaff in this build.) As previously mentioned, casting a spell of an opposing school of magic to your own costs more Mana, and can fatigue you, so keep that in mind.