The Grim Brigades hero slayer, is also very good at sieging and pushing. His only flaw is that he's rather fragile, as an intelligence melee hero.
Static charge: And amazing default skill. Make sure to buy the talent to level this up to maximum. Charges up as you walk around, and at max talent level it charges up pretty fast! I once got an early kill by avoiding being hit for a couple of minutes, then a hero attacked me and got hit for 900 damage and died...
Ion Surge: Turns the target ethereal for 4->7 seconds. You will do evocation damage when you attack the target. This is MASSIVELY powerful, since in a group fight the ethereal status means your enemies will take a lot of extra damage from spells. Futhermore, they can't attack, but you can attack them! And... your attacks hurt. A lot. On top of that, any unit which does MAGIC DAMAGE can still attack the enemy hero, in fact they will also get increased damage from ethereal status. Very useful with Frost Wyrms.
Polarize: Damages both the target and surrounding units, based on units being near target. Very useful pushing tool when used against large groups of enemies. Has a low cooldown so can be cast on several targets at once. Can also be used against heroes, but a lot less useful since it doesn't last as long, and heroes aren't usually stupid enough to stay next to allied creeps and get fried.
Streak: Semi-blink+ AOE stun. Quite a useful skill, since stun is 2 seconds.
ThunderStrike: Not a hero killing skill, yet VERY powerful under the right circumstances. You cast it on a single target(friendly or enemy, structure, unit or hero) but enemies in an AOE are silenced AND receive a miss chance from 50% to 95% at max level. Lasts only a 8->12 seconds (1/2 duration on heroes), BUT when cast on a structure will cast itself again every 4 second. 5 times at level 1, 9 times at level 6. Meaning a 95% miss chance + silence for 35 seconds in an AOE around an enemy or friendly structure? VERY useful. To make things worse, also does significant damage to enemy structures. Cast it once, and wait for the tower to be hit 1+9=10 times, for almost 100 damage each time? Niiiice.
StormSpire: This heroes ultimate. Sort of underpowered and doesn't seem to work properly for Polarize. In THEORY, it should be adding around 50 damage per strike when the spire has 500 mana, but it doesn't seem to be working properly at all. Gives a nice bonus damage to Static Charge though. Not very useful to be utilised for Thunderstrike, since the duration of a normal thunderstrike is long enough, and anyhow, there's more than enough normal structures to be utilised. The other notable contributions of the spire to your team are increased speed for your units, and the fact that Streak can go through it at a longer range than most targets.