Kel'Thuzad is available on the ptr

This guy seems like he was worth the wait. Not only does he look cool but he's one of the coolest Warcraft characters ever. He's an important character in classic Warcraft lore. He has two raids in World of Warcraft and set Arthas on the path to become the Lich King. In addition, he was one of the original Undead units from Warcraft 3. Here I'd like to go over his abilities which mostly seem like skillshots. You can test him out on the ptr right now if you have the gold to purchase him (15k) but he will probably be released sometime soon on the live servers. He's already been on the ptr for a while at this point. I'm just going to cover the abilities for simplicity's sake.

His trait is Master of the Cold Dark
Quest: Gain 1 Blight every time a Hero is Rooted by Frost Nova or hit by Chains of Kel'Thuzad. 
Reward: After gaining 15 Blight, the cooldown of all Basic Abilities is reduced by 2 seconds. 
Reward: After gaining 30 Blight, gain 75% Spell Power. 

This looks like a great trait mainly because of the 75% spell power. I bet once you get that you can insta-kill many heroes in the game easily. The cooldown reduction isn't all that great to me but the spell power is something that is really powerful. 

Death and Decay (Q)
After 0.5 seconds, launch an orb that explodes upon hitting an enemy, dealing 150 damage to enemies in the area. The explosion leaves behind a pool of decay that lasts 2 seconds, dealing 70 damage every 0.5 seconds to enemies.

So this appears to be a skillshot that does good damage. A good bread and butter attack for general use, wear and tear, and finishing blows.

Frost Nova (W)
Create a nova that explodes after 1 second, dealing 212 damage to enemies inside and Slowing them by 35% for 2.5 seconds. Enemies in the center are Rooted for 1 second.

This is an attack that you'll probably want to use a lot once you get close to enemies. It helps a lot with your trait so I'm guessing you're suppose to use this a lot of heroes, probably combo-ing it with q and e abilities. You could frost nova someone thus rooting them, then death and decay shot them, and possibly throwing out the chains of kel'thuzad attack too. A basic combo seems like frost nova then death and decay. 

Chains of Kel'Thuzad (E)
Launch a chain, dealing 97 damage to the first enemy Hero or Structure hit. For 4 seconds after hitting an enemy, Chains can be reactivated to launch to an additional enemy, pulling both enemies together and Stunning them for 0.5 seconds.

I'm not sure if it works the same way but this kind of reminds me of Roadhog's hook from Overwatch. Actually reading it again I know it doesn't work the same way, as this attack stuns multiple enemies if they are both chained. Interesting attack but it seems very situational, ie team fights mostly.

And his Heroic abilities aka ultimates
Frost Blast (R1)
Launch a meteor of ice at an enemy Hero. Upon impact, the meteor deals 100 damage to its target and 275 damage to enemies in the area. All enemies hit by Frozen Tomb are Rooted for 1.5 seconds.

This seems like the ultimate I would go for every time with this dude. It's got a lot of dps and it roots people too! Too good to pass up, that's for sure.

Shadow Fissure (R2)
Create a fissure anywhere on the Battleground that explodes after 1.5 seconds, dealing 440 damage to enemy Heroes in its area.

This also looks like a good choice but the fact that its probably only going to hit a certain particular area means I wouldn't go for it too often unless the enemy team was bad at positioning and I noticed in particular that it was so. But a fissure does sound awesome!

Alright so that's gonna do it for Kel'Thuzad's abilities. He seems great! I've seen gameplay and it seems like you have to hit pretty much most of the time to get the most use out of his trait and just in general to play like really well. If you can't land skillshots the majority of the time then its going to be difficult playing him. At least it seems that way. We will have to wait and see what he's really going to be like once he hits the live servers.

For the Lich King!