Zoltan Kulle is in a unique position as Diablo bosses go; comparatively speaking, he’s actually a good guy. A megalomaniac, sure, but his primary goal is to free humankind (nephilim) from the dominance of the angels and demons and empower the race as a whole (with him at the top, but still). Heck, he even warns you that your allies ‘seek only to use you’ and offers to share his power. Unlike many megalomaniacs, he’s actually telling the truth with his warning, and while his goals aren’t entirely selfless, they’re remarkably positive for someone you’ve got to fight in a Diablo game.
That said, you’re still gonna have to kill him.
Unfortunately for you, he and his two friends have rather a lot to say on that matter, and quite loudly.
Zoltan Kulle is accompanied by two large unique golem-demons. While most of the time you will have to kill them to get uninterrupted shots at Kulle himself, it is possible to come back at a later level and ignore them, or do so as a single member in a larger party. The golem-demons are pretty simple, being essentially larger versions of the ones you faced in earlier ruins, though they have the added benefit of not only more knockback, but longer stagger animations attached to being hit with their fists.
The real danger here is Kulle himself. Taking a page not only from the Wizard, but also from the Diablo II ‘Summoner’ type enemies, Kulle glides around rather quickly, launching fireballs and tornadoes at you. The tornadoes move randomly but slowly, making them easy to avoid. His fireballs are harder to evade, being simple, straight shots, but they aren’t terribly damaging.
The most interesting and actually most dangerous thing at Kulle’s disposal, though, is his time-bubbles. Usually maintaining at least one at any given time, Kulle will create bubbles of slowed time several meters across, usually centered on you or one of your allies. Everything in those bubbles happens slower- projectiles fly slower, you move slower- but things standing next to them are not affected. This causes you two grievous problems.
First of all, with the roof caving in slowly, standing in a time bubble makes it fairly difficult to avoid getting conked on the head by falling masonry. Not the most terrifying prospect, but still fairly damaging.
More importantly, Kulle’s golems are large enough that they can reach in and bash you without standing in the slow-time bubble themselves. Because of this, usually you’re going to want to take out the golems before bothering with Kulle; he actually isn’t all too terribly damaging. Must be all the time he spent dead.
