Titan's Realm is the tenth level of Doom (2016). There are six secrets, two Elite Guards, one Field Drone, and one Argent Cell located in this level. Rune Trials are absent from this level onwards. It is also the second Hell level. The mission name is the same as the level name.
After the disastrous Project Lazarus Manned Expedition (MTC 2145/128) it was decided to avoid Kadingir Sanctum until the environment was more conducive to human exploration. The second Project Lazarus Manned Expedition (MTC 2148/177) was changed to a new location - an area referred to as "the Great Steppe". The Corrax tablets describe this area in detail:
"Through the Titan's Realm and down, down to the Great Steppe where the trophies of victory are kept through the ages. Their false idols banished to a wasteland. Their towers fallen, their foundations ground to dust, and their hallowed halls kept empty as cruel reminder that civilizations shall fall before the ascension of the great ones."
If you are one of the lucky disciples who will get to experience a pilgrimage to Hell, there are some precautions you must take for your journey. You must make sure all your affairs are in order before leaving. Donate all of your belonging, excluding any security controlled materials, to a Tier 2 advocate and record any final logs you may wish to make. Your savings and assets will be used to fund additional UAC research. You the expedition itself, you may wish to consider sedation; advocates can get overwhelmed during their transition and a medically administered balancing agent may help ease the excitement. Lastly, prepare your mind for the wonders you will experience. Seeing the remains of a Titan is an experience that will buckle the knees of the most steadfast advocate. If you are lucky, you may even get to see a live Titan. If you do, you must record the sighting immediately and hand you storage devices over to a Scout-Bot for safety. It is not known if any Titans still inhabit the Great Steppe, so if you get the chance to be a sacrifice to one of these massive beasts, take it!
Titan's Realm occurs in a darker, "nighttime", more foreboding section of Hell than the Kadingir Sanctum, which occurred in "daytime". Near the beginning, the player must jump down into the literal open mouth of a cave carved into the shape of a demon's head into an underground cave complex filled with gigantic bones and fight his way into an underground stone castle whose entrance is also shaped as a demon's head, and much of the ground in the entire level is covered in what appears to be blood and other red organic matter. Radioactive green slime, which ironically enough never occurs in any of the UAC levels, is also more common than it was in Kadingir. The underground stone castle which takes up most of the level also contrasts with the mainly-outdoor Kadingir, and with its many broken stone stairwells, the interior of the castle bears some resemblance to the labyrinth used for many of the Rune Trials.
- Trick Shot - Kill a Lost Soul with another Lost Soul.
- Atop the Mountain - Perform a "Death from Above" Glory Kill on a Baron of Hell (attack from above).
- Dominator - Kill 20 demons while using powerups.
- Learning about Titans from the Slayer's Testament statue and the data log may be intended to lead the player to a ghastly realization: that the beginning of the level is an enormous gruesome burial site where a Titan was buried up to his neck; and, it would appear, suddenly and violently. The player actually jumps down into the throat of the Titan's rotting corpse, the monstrous bones are the Titan's spinal column and rib cage, and the blood flowing like water is actually the giant demon's real blood. The blood, bile, and stomach acid from the corpse have subsequently seeped into the underground cave complex into which the rotting body was inserted, as well as the stone fortress within the cave complex that makes up most of the level. And because the Testament in the fortress states that the Doom Slayer killed a Titan, it is even possible that this is in fact the remains of that same Titan. (See: The Titan)
- The weather overhead at the beginning of the level looks very much like a cloudy late evening on Earth with a thunderstorm off in the distance. No planets can be seen overhead.