Venril Sathir is the only boss named found in this instance. He is a hovering Sathirian with a bad attitude.
The key to this fight is not Venril himself, rather it is your raid paying attention.
Venril has a 8% chance to cast fear on any dmg to him. The fear the doesnt last long at all, roughly 2-3 seconds. However, this fear can be deadly if your healers are dps'ing. Ensure healers only heal and dont do damage of any kind.
You must do this fight with one person devoted to click the statues in his room. The statues are located on the floor behind his platform, one on each side. The statues can be clicked from his platform. These statues must be clicked constantly during the fight to prevent the two larger statues in the hallway leading up to his room from spawning. If you go too long with out clicking them they will activate.
With that said, Venril has a trigger chance at 90% to spawn the statues immediately. Your raid must try to time the clicking of these statues at this time. Make sure both statues have just been clicked and then burn past 90% to ensure the statue's will not become active.
During the fight Venril will cast Toxic Infusion, which is an AOE that is on a random timer. The timer has been timed to atleast be 19 seconds in a recast and upto one minute at times. If Toxic Infusion is not cured off your groups it will explode the hearts of your raid members. You have 6 seconds to cure this Noxious effect from your raid. If you are not capable of having 4 group curers in your raid, then you must bring plenty of Cure Noxious pots with you, otherwise you wont last long.
The second trigger chance during this fight occurs at 65%. If you have not obtained the "box" from the Thugga raid encounter then you wont be going much farther in this instance at this time. At 65% Venril will emote how will finish this fight, if the box is not placed on him within 5 secs, he will explode your raid. The easiest way to get through this is to have all your big hits ready at 70% and then at 67% burn him hard through 65% and have the person with the box in the raid spam it on Venril until its on him.
At 60%, with Venril's main ability disabled, he will begin to watch your power consumption. Your raid force must keep their power within 30% and 60% to be safe. If a raid member goes over or under these ammounts it has a chance every 2 seconds for venril to notice you. Over 60% he will strike for Magic Dmg and take your health to roughly 5-10% of your total health. If you go under 30%, it will summon a Epic x 2 add that will wipe your raid. They hit very hard.
What to watch for
On top of just maintaining your power, Venril will also place 2 kinds of effects on 2 random members of your raid about every 45 seconds. These effects last for about 10-12 seconds. Mana Sacrifice is the main thing your raid members must be looking for as well as a Power Feed (need name).
Mana Sacrifice is an effect that when you use an ability it will consume roughly 200% more power than usual. Remember, if you go below 30%, you can spawn the add. This is the main cause of failures in Venril's Lair. Do not use any abilities that use power while this effect is on you. If you can, turn up your particle effects because you will glow 'BLUE' when Mana Sacrifice is on you. If you are in the middle of casting anything and the effect lands on you cancel it immediately.
The other ability (need the name) is a power feed. Which will give enhanced regen to the person it lands on. A feed of about 1% power every 2 seconds for 10-12 seconds. If someone is not paying attention or just sitting there, they can get hit by the bolt if the feed gives them too much power.
An easy way to keep your power down, is to toggle Sprint on and off if you hit 60% power. This should bring you to 45% power and keep you safe. Do NOT hit sprint when you have mana sacrifice on you, it will drain you completely. (reminder - the person clicking the statues, must also have their power between the said amounts and keep an eye on their effects as well.)
So, on top of these added effects at 60%, you still must keep up with the curing of the Poison AE, Toxic Infusion. Be on the lookout for Venril Sathir's random 'reflect' as well. Classes in your raid casting group poison/disease debuffs can appear to be "toxic infusion", when it really is not. Venril will also cast a close range Trauma Stun on members nearest to him. This effect last only for a few seconds but seems to only affect a certain number closest to him. To ensure healers dont get stunned, place all dps infront of the healers.
It sounds stressful and it is, but Venril should not straight up kill your tank. The success of your raid depends on people paying attention to their 'Detrimental Effects' window and thinking fast.
Good Luck.