Since this is a boss map, it is advisable to recruit (or replace) every single ally. If they are not unlocked, this is the last chance to go back and fulfill the requirements to unlock them.
In the winding hallway leading down to the lake of blood, there are two easily overlooked side paths, each containing an enemy and some items. If the player goes to the boss room without clearing these, there will not be any chances to go back, resulting in an incomplete kill or item count.
Average Payout: 10,000 credits
Secrets
1. The perimeter wall of the starting chasm is lined with indentations. When nearing the top of the thin sloped walkway, carefully jump into the closest indentation to the northwest and open it for a secret teleporter. This leads to a cage in the hell nobles room with some potions.
2. The room with the annihilators has two secret alcoves behind false walls, high up near the ceiling (but they will not be accessible until all the annihilators are defeated). Pressing each switch will summon potions next to the row of health bonuses. The first secret is in the center of the south wall.
3. The second is in the northeast, on the north wall.
Rings
59 After lowering both rows of bars blocking the large green teleporter to the boss room, the ring is visible in an alcove to the left. To get inside, the player will need to press two switches in the starting chasm that are rather hard to reach. The goal is to get on top of the wide ledge surrounding the lava chasm, and there are two possible methods:
One is the sandbags trick. Throw them down into the lava so that they can be dropped down onto, then put Iron Prison around them. Put the next sandbags a short distance away, jump to them, wait for Iron Prison to recharge, cast it on the sandbags again. Repeat the process until the lava is crossed, and then mine + rocket jump up to the ledge.
Two involves walking along the edge of the lava without actually touching it. Turn on chasecam and carefully drop down onto the edge of the lava falls so that the player's sprite overhangs the edge and doesn't contact the surface. Now slowly maneuver along the edge of the lava falls until reaching the side of the chasm, right underneath one of the switches. Place sandbags on the next level below and drop onto them, then mine + rocket jump up to the ledge.
Either way, there is a trigger line running all along the back of the ledge against the edge of the map. Stepping on it causes a walkway to rise up, providing a much safer way of getting back.
Secret Ring #4: Purple
This ring is behind Kranium in the boss room. Distract the boss with summons, run around to the back of the cross structure, and mine + rocket jump up to the back ledge.
Boss Strategy
Kranium is a variant of the Icon of Sin and the battle will play out like the final battle of Doom II, except for a few key differences. The player can aim more precisely at the weak point and damage the boss with any direct fire weapon, but Kranium has a lot more HP than the Icon of Sin and will require a lot more damage to destroy. The boss can summon a massive swarm of minions, but so can the player. Make liberal use of Clock Freeze and summon every last ally to buy time.
Get the final secret ring (see above) before things get too hectic, then go back and get the potions on the stairs. Wall jump to the top, cast Invisibility to avoid enemy projectiles, and aim for the weak point. A well-aimed Electric Destruction can take off a large chunk of the boss's HP, and rockets and plasma shots can deal damage while waiting for it to recharge. Kranium is worth 2,000 XP when destroyed.
