I had that problem too on a new toon. My advice: leave the main story for now and level up a bit first through exploring and questing/delves/ect.

Once you get more passives/stronger skills and have higher tier gear. the fight should in theory be easier.

Resource management is important when bosses give you trouble. Make sure your weakest resource pools (magicka/health/stamina) are suitably offset with armor/weapon/jewelry bonuses, or buff with food/drink/potions.

Level up until you unlock weapon swapping, and get the bow as your back bar (secondary) weapon. You can rapid-fire spam the bow's light attack, which is really effective at keeping K'tora off-balance, which limits the spawns of orbs and additional enemies, and limits opportunities for the annoying self-healing. Keep the onslaught up and you'll chase the boss back and forth across the field more than anything, whittling away at its hit points. It takes a while.

xFoundProspect wrote: »

I don't really have anyone to play ESO with so I've been trying to take out K'Tora on my own, but he's the most difficult boss I've fought so far. I'm a level 9 nightblade any tips for me?

Level up to 15, because you need weapon swapping. At level 9 NB, you don't have much in the form of DoT (damage over time), and the bow is helpful for this (poison injection is extremely helpful).

Also I got really close to killing him once but he just regenerated half of his health in an instant... what ability does he use to do that and is there any way to counteract it or at least minimize the healing?

If memory serves, he's spellcasting to restore his health.

If you watch enemies closely, you'll see two types of effects:
"Yellow" shimmers (which look like yellow sparks coming off the enemy) denotes an attack is about to occur. If you block, you mitigate this attack and knock the enemy off balance. Using HA will knock them over.

"Red" shimmers denotes a spell charge, and you must bash, not block!, to interrupt this. Doing so stuns the enemy, and stops the spell. You should see "Interrupted!" pop up if successful.

Practice a bit more until you recognize these signs, because blocking/bashing are very important skills to learn and require practice.

Hope this helps.