@StreamSide these bosses aren't like the bosses of warzone 1/2/3. The bosses of warzone 1/2/3 don't really require you to do anything except for killing it as fast as you can. The bosses of warzones 4/5/6 however have some things you need to do before you can kill them. Here is the video/explanation of every boss:
Warzone 4
Start the fight by attacking the The Baron from Below. After some seconds, it will change into The Hungry Baron from Below and teleport itself to the center of the room (meaning trapping it on corners is futile), and an Organic Matter will spawn. At this moment, the whole team should kill the Organic Matter as fast as possible, otherwise The Hungry Baron from Below will devour it and recover half of its maximum health. When the Organic Matter is destroyed, 4 Aggressive Matters will spawn. Kill them fast as well (AoE recommended) so you can focus back on The Baron from Below. Note that you'll have to target the boss again after every shape change.
Watch out for the 4 Lava Holes in this room as they will become active (just one at the time) for about 4 seconds and explode dealing ~1500 hp fire damage, it has the same area as a Great Fireball Rune.
Inside the room, you'll also find Aggressive Lavas which use an area fire spell on themselves. These must be kept far from the boss, because it gets healed by Fire Damage. This also means that other Fire spells and runes (such as Hell's Core and Great Fireball Rune) shouldn't be used, as well as Emberwing which deals Fire Damage.
Inside the room, you will find The Count of the Core. The Count of the Core is also healed by Fire Damage, and inside its room there are 5 sets of aligned Obsidian Pipes that will throw a Fire Wave towards the other side of the room, healing the boss and dealing massive damage. The easiest way to avoid this healing is to block of the Obsidian Pipes by throwing Magic Wall Runes in front of them. Using this strategy, the boss can be trapped on the south-east corner of the room and one or two team members can be responsible for renewing the Magic Wall protection when the Pipes are about to fire (they glow for a few seconds before that).
The team must also watch out for Snail Slimes which will constantly spawn as the boss gets hit. They should be killed far from the boss, otherwise The Count of the Core will also be healed upon their death and the players will take about 1000 damage upon each Slime death. The easiest way to do that is to have a second blocker use Challenge on them and keep them away, and then the team can attack the Slimes from distance with Avalanche Runes.
Finally, you will have to deal with Ember Beasts as well. Those apparently make The Count of the Core stronger upon dying, regardless of them being close to the boss or not (The count absorbs the power of the beast and becomes stronger). Thus, you can try to block and avoid damaging them, but they will likely die when the team attacks the Snail Slimes, though this shouldn't be a problem.
Inside the room, you will find The Duke Of The Depths. During this battle the duke will turn invincible (The Fire Empowered Duke) and Fiery Hearts will appear in 5 fixed at the center of the room. The team must kill all of them quickly will make the boss vulnerable again. If the Fiery Hearts aren't killed fast enough they will become a Fiery Bloods, very strong Fire Elementals that you will also have to kill. One possible strategy is to split the mages of the team in two groups which should take turns in using their ultimate spells (Energy/Ice) to hit all Fiery Bloods and destroy them quickly, while the other shooters attack them with AoE spells and runes.
The boss can be trapped and blocked by only 1 knight in the east of the room near the teleport, but this blocker should be a high level because during the time The Duke Of The Depths becomes invincible it also becomes much stronger, dealing combos of more than 4000 hp, so at least two Druids should focus their healing on the main blocker. The Duke will use its strong waves when its attacked while invulnerable, so this should be avoided at all costs. Other knights in the team can help blocking the Aggressive Lavas that will be spawning in the room during the battle. Beware that the boss' strong Beam and Wave have a large area, so all players should mind their positioning to avoid taking this high damage.
Ancient spawn of Morgathla
After defeating all 3 Warzones bosses, you'll have the chance to battle the Ancient Spawn of Morgathla. To start the fight, you'll need the three pieces of a strange mallet (mallet head, mallet pummel, mallet handle).
Note that only one player needs the Mallet for the whole team. With the pieces in hand, use the Huge Red Crystal on the floor just under Gnomus, here, to be teleported to a room with NPC Gnominimus. The player in possession of the Mallet pieces should talk to the NPC and have him build you a complete Strange Mallet.
The access to this boss room is similar to the Warzone bosses, meaning that teleport will only stay open for some seconds and all players must enter it quickly. To open the teleport, the player who has the Strange Mallet must use it on the Gong and you will see the message BOOOOOOOONG! (Attention: the Strange Mallet will break and disappear once used, so make sure your team is ready to go before doing so). The stone next to it will turn into a Magic Forcefield and all players should enter it quickly.
This battle happens in 4 stages, each one in a different room. Despite that, all stages consists of pretty much the same thing with increasing difficulty. Initially, many Burrowing Beetles will spawn in the room. They are much stronger than regular Scarabs but can be killed quite easily (they do deal considerable damage, so watch your health and mana). The recommended strategy here is that the team positions in one of the corners of the room in a way that the most vulnerable players (lower level paladins and mages) can be protected (see the image gallery below). On the last room, Wild Growth Runes can be used to also protect the team due to the high amount of beetles.
Once the Burrowing Beetles stop spawning, the Ancient Spawn of Morgathla will spawn. Initially the boss will be immune and heal if attacked. In order to make it vulnerable, lure the boss onto one of the crystals inside the room while they're blue. After doing that once the boss will start taking damage again. Mages can use Sudden Death Runes and everyone should focus only on the boss.
During the first 3 rooms you have to attack it until it disappears, and on the 4th room it will die.
Note¹: Inside all rooms there will be Sulphur Geysire which will constantly deal Earth Damage around them (the area increases every turn) and can hit up to 1500, an from the second room on there will also be Obsidian Pipes that, once they start glowing, explode dealing 2500 Fire Damage. This damage, combo'ed with the boss damage can instantly deal over 5000 damage, making the fight very dangerous.
After defeating the boss, enter the teleport to the north (be careful if you linger in the boss room because the Geysers keep exploding). Open the chest to receive the Scourge of Scarabs achievement. There are three different reward rooms:
