Azmodan’s companion of choice, Cydaea is unique in Diablo games as a whole for a single reason- she’s the only boss you will find yourself fighting twice.
Dangling from the ceiling on a web-line several times throughout your delve into Arreat Crater, Cydaea seems to draw a lot of pleasure from taunting you with vague hints and plentiful innuendo. She doesn’t actually drop down to meet you until you reach the first Heart of Sin, where you will first cross blades with her.
She appears more after that, finally coming to fight you again at the second Heart of Sin, where you finally slay her. Despite lacking in health and power compared to Azmodan’s other underlings (especially Ghom and the Siegebreaker Beast), Cydaea dishes out a hefty bit of damage and difficulty not through raw power but through frequent attacks and three abilities that are bothersome individually and collectively very damaging.
First of all, Cydaea will frequently spit a spread of poisonous missiles out. While they don’t leave any traces or otherwise inconvenience you, it’s more damage than you want and allows her to hit multiple targets simultaneously. Their damage isn’t too terrible, but she launches them pretty frequently.
Secondly, as with Spider Queen Araneae, Cydaea will launch masses of sticky webbing at you. These do splat on the floor, leaving an area that heavily reduces your movement speed. Since these are usually right between you and her when they aren’t centered on your feet, they can make things particularly hard on melee characters who don’t have a handy way to escape.
Finally, Cydaea creates tiny pools of putrid-yellow tinged darkness on the ground, from which crawl large numbers of spiderlings. Though the spiderlings are individually negligible and cannot individually deal much damage, each pool will spew several per second over up to ten seconds, and if you aren’t prepared to regularly clear them away from you, you can find your health quickly dwindling thanks to being mobbed by the tiny creatures.
On top of all this, Cydaea will, as with the Spider Queen in Act I, sometimes vanish up to the ceiling for a brief period. She will usually do so when several spider-spawning pools are laid out on the ground, leaving you to briefly deal with only a mass of tiny spiders nipping at your legs.
Cydaea is a highly mobile enemy, and melee combatants will frequently find her retreating from them, which can make her fight a bit aggravating. On the other hand, ranged attackers will find themselves quickly overrun by her summoned spiders as she tends to create summoning pools much more frequently when at a range. While not the most challenging of bosses in the game, this makes Cydaea an opponent you need to keep track of, and find a way to keep on without letting yourself ignore what’s around you. Dying to tiny spiders is surprisingly easy, and really is the main threat she presents.
