Just did this mission with a full group. It appears that you are on a timer, didn't see how long. First attempt we didn't move fast enough and more halflings than you can count started running through the zone and wiping the group. Once the emotes go off for them to start attacking, mission ends. Second attempt we had One person pull, one person tank, one person healing. Healer loots the first ten brains, five to heal and five to give to the tank to keep pets up. Once healer has 5 brains, the rest of the group loot 3 each so they can back up heal as needed. Just keep killing until you get the 80 brains looted. Have the healer give the tank 5 brains to summon more pets when they poof or die. Chest drop was Gore-Covered Tombstone Shard, HP +30, AC +20 type 7 aug fits in most gear slots including weapons. Only had one death, make sure everybody assists MA because of the healers. Also, you get a self buff that last two minutes, it appears to increase damage. Also get a dot to cast, use it because the halflings will run at around 10 percent.