This page of the Mutant Year Zero: Road to Eden atlas contains a detailed walkthrough for The Grogg Den. This location contains a large number of pyroghuls that utilize fire attacks to hurt your party. Our guide contains information what kinds of mutants can attack the party in The Grogg Den and what treasure can be found in the area.
The Grogg Den - basic data
Opponents - Pyro (level 35), Med-Bot (level 35), Pyro's Commander (level 35), Hunter (level 35).
Suggested level - 35.
Connects to - Cultlands (always available).
Unique loot - Elysium - LR 678 - One of the most powerful weapons in game. LR 678 fires powerful laser charges that have long range, can destroy covers, and doesn't have to be reloaded.
Loot - Artifact - Grogg Milker. Note - Fishmas Bill. You can also find a lot of Molotov cocktails.
The Grogg Den - combat and unique locations
The barn area is patrolled by a Med-bot - consider destroying it at the beginning of the battle, so you'll have one less opponent to worry about during the actual combat with the ghuls.
The map contains a lot of Pyro opponents - you need to be wary of the fact that your men can often be set on fire. Consider equipping Pyro Armour (if you have one) and taking a supply of smoke grenades that will enable you to douse the flames quickly.
You'll encounter Pyro Chief, an elite version of a Shaman. Most likely you won't be able to kill him at the beginning of the combat, but try to get rid of him before he calls for the second wave of reinforcements.
Stay close to the barn, as an attempt to leave it may be countered by Hunters with activated Overwatch. As always in the case of facing Pyro opponents, scatter your men, as a single attack from a pyroghul may set more than one of your party members on fire.
Search the whole map once you win the battle. You can find a lot of standard loot and there is a chance of an enemy dropping a weapon upgrade. Moreover, you can find a note, an artifact, and a large supply of Molotov cocktails.
The most valuable item (Elysium LR 678) is found in the chest shown in the screenshot above. The weapon offers 9 damage, 15% chance of critical strike and has a range of 14 squares. Moreover, the weapon doesn't have to be reloaded often. Upgrade it by spending weapon parts after you return to the Ark.