This is event has to be triggered. There is a large untargetable worm called "The Burrower Beast" that needs to be up to trigger this event. This is reported to be trackable. The Burrower Beast is in a small dead end side passage from a room that has no mobs in it. To get to the room from Echo Caverns, cross the invisible bridge. Bear left once you cross the bridge, and take the first passage on the right opposite the fake bridge. Bear right at the T junction and take the first left. This takes you into the event room. Be sure that everyone keeps right as they enter the room and stays on the rocks to the right. This will enable everyone to arrive and prepare without triggering the event. You should see The Burrower Beast in the passage opposite from this vantage point.
Preparation: Standard melee buffs. None of the mobs in this event will cast anything.
To trigger the event, approach The Burrower Beast. I found it best if the whole raid approaches The Burrower Beast and settles on the top of the small ramp to it. Place your best tank in the middle of the main room to grab aggro on the spawning mobs. It is important to keep someone in the centre of the room, otherwise the event will reset. If the event resets, have everyone leave the room and enter again. All the while the event is running properly, there will be an untargettable "massive burrower" blocking the exit. This massive burrower will hit for damage and has a knockback effect to prevent you from leaving the room. However, if the raid clings too close to the room walls to avoid aggroing spawns then the system thinks that you have wiped and resets the event. Apart from rock burrowers, none of the mobs in this event call be mezzed or slowed. When you approach The Burrower Beast, you get this message:
The ground shakes momentarily. You sense motion beneath the surface on
which you are standing.
This message indicates that the event has been
triggered. 45 seconds later, you get another message:
The giant burrower roars, causing the ground to rumble. You begin to
sense movement around you.
This announces the spawning of 3x spined rock
burrower's, 3x stone carver and 6x rock burrower in the room (12 mobs). You
have about 4 minutes to kill these before the next wave arrives.
The giant burrower begins to thrash in the narrow tunnel and the ground
erupts around you!
This announces the spawning of 5x stone carver and 8x
rock burrower in the room (13 mobs). You have about 5 minutes to kill these
before the next wave arrives.
The giant burrower roars again... the sounds of smaller beasts fill the
room with a reply!
This announces the spawning of 3x spined rock burrower's,
5x stone carver and 6x rock burrower in the room (14 mobs). You have about 5
minutes to kill these before the next wave arrives.
The giant burrower enhales deeply befre releasing another great
roar!
This announces the spawning of 6x core burrower's in the room. You
have about 5 minutes to kill these before the next wave arrives.
< No announcement text seen. Was I standing in the wrong place?
>
Now 6x core burrower's spawn in the room. You have about 5 minutes to
kill these before the next wave arrives.
The giant burrower slams against the walls of the tunnel, filling your
nostrills with the stench of fresh earth and rock dust!
This announces the
spawning of 6x core burrower's in the room. You have about 4½ minutes to
kill these before the next wave arrives.
The giant burrower roars in pain, releasing a foul current of air!
This announces 2x parasite larva which spawn in the tunnel behind the
Burrower Beast. This is the last wave before the boss mob. The final mob is A
burrower parasite which will drop the loot that the raid wants. This will spawn
at the back of the passage behind The Burrower Beast about 10 minutes after the
Parasite larva spawned. This message gives you about 10 seconds notice of its
arrival:
The giant burrower begins to tunnel into the ground below it. As it digs, its flesh splits revealing an enormous parasite!
The burrower parasite has lots of HP and regen and will quad for 1100. Its very resistant to poison and disease, and to a lesser extent magic.