A rather complicated/hard boss for most newer guilds in AQ40, took a while to down for most guilds the first time. For a while people thought he wasn't worth the time/consumables, some still think so.
Poison Volley: AoE spell deals 1500 nature damage(Nature Resist helps) Also does 500 natures damage every 2 seconds for 10 seconds. Can be abolished.
Toxic Cloud: Viscidus spits these out, they are rather hard to avoid and deal 1500 damage every 2 seconds. Also slow your run speed to 60%.
Poison Shock: Deals 1200 Nature damage every 10 seconds, 15 yard range.
Parts of Viscidus: 20 spawn when Viscidus is shattered, each has around 10,000 HP.
Viscidus has 3 stages of Freezing and 3 stages of melee. Each stage has an associated emote allowing you to tell what stage he's in. Here is a list of the stages and the emotes:
Viscidus begins to slow: 15% movement/attack speed reduction
Viscidus begins to freeze: 30% movement/attack speed reduction
Viscidus is frozen solid: Viscidus stops moving/attacking
Viscidus begins to crack
Viscidus looks ready to shatter
Viscidus explodes: This spawns the 20 mini-viscidus oozes
Station your raid groups in a circle around the room, position Viscidus in the center. Have your melee groups stationed at the edges to avoid his AoE attacks. When Viscidus begins freezing have the melee groups move in.
Make sure each group moves out of the poison clouds as soon as possible. Have all classes capable of removing poison doing so throughout the fight.
You will have to freeze Viscidus with cold damage spells/items such as frostbolts and cold damage items/weapons.
When Viscidus freezes have all casters bandage to conserve mana, melee moves in and hammers on him till he shatters. He has a timer so make it fast.
When Viscidus shatters he spawns 20 mini-oozes, focus fire each ooze one at a time. Some guilds use the MT to target, others have half the raid on one, the other half on another. You have around 10 seconds or so before the oozes reach the center of the room to reform.
The general number to shoot for is 5-6 oozes per shatter, each phase becomes a bit harder to stand with more toxic clouds. Other then that it's endurance, good luck.