Here are some ideas for a death knight class;
pick and choose which abilities would work well together and what one would be the ultimate...

Abilities:
Death Grip - pulls an enemy within [x-y] range to your location.
Blood Worms - spawn [x-y] blood worms that leech [z] health from a nearby enemy
Minion - call fourth an undead minion to defend you for [x-y] seconds
Corpse Explosion - any enemy killed by you will explode for [x-y] dmg
Icy Shackles - slow enemy movement to 10% for

• seconds (they slowly regain speed)

Plague - deal

• damage over [y] time to an enemy when shot

Death and Decay - enemies standing in the area of effect take

• damage per second, lasts [y] seconds.

Fortitude - freeze your blood to reduce incoming damage to

• % for [y] seconds

Blood Rune - instantly heals self by

• hp.

Blood Boil - all nearby enemies take

• damage

not sure if this would be a knife only race, could be a tanky knife race. with death grip and icy shackles it could work well,

would be interesting to see some feedback on this idea, needs more input though,

For Ownz...

And I think this sounds like a great race, but balancing I agree might be tricky.

Death Coil
A coil of death that can damage an enemy living unit or heal a friendly undead unit.
-> Simple extra dmg.

Unholy Aura
Increases the movement speed and life regeneration rate of nearby friendly units.
-> Either simple extra speed or speed aura.

Death Pact
Kills a target friendly unit, giving a percentage of its hit points to the Death Knight.
-> Maybe sacrifice ammo for life or same but other way around. Or maybe get "no reload" for 50hp.

Animate Dead (Ultimate)
Raises 6 dead units in an area to fight for the Death Knight. Animated units are invulnerable.
-> I'd say raise 2 dead team mates for about 10  secs. Either invulnerable or not.

Original war3 skills of death knight.

Then death knight race is not the best idea for a new race
Resurrection is mainly the thing the war3 death knight is about.