There will be elevator doors from where you begin however attempting to pass initially will only cause some blood goats. Afterwards, there will be plenty of enemies inside of the elevator that gives you a great chance to boost up your Stylish Rank. At the end of the path beyond the elevator, This room will send out red orbs at you but be sure to avoid them because they will teleport you into an area with Savage Golems. At the end of the room, there should be a Sacrilege. On your way back, there should be a door right under where the Sacrilege would be on the lower floor for a Secret Room. Around the balcony should be a blue orb fragment. Make your way out and don’t mind the pyromancers unless you want to raise your orb rank. Run along until you reach the fork in the path but take the one closest to you where you’ll face Bolverk (just use the same strategy as before). Get the Sacrilege again and get out back into the hallway. There should be a room that holds a blue device that summons Abyss Goats once activated. After this fight, Frost Heart is available and return to the hall. Find the path lined with red orbs (this one is found between the route to two other rooms) where after more enemies, will leave you with another elevator with more enemies. Through the door is a cutscene with a new boss.
To defeat Trismagia, wait for it to split in three, then begin shooting all heads. These heads are each one of a color, and each one has its color and elements:
- The Blue, happy face attacks with lightning balls from afar, and thunder rings when it's close.
- The White, sad face attacks with ice balls or/and ice pillars from afar, and an icy cloud at close range.
- The Red, angry face attacks with fireballs from afar, and explosions at close range.
To defeat Trismagia, you must discover which head is the true one, by shooting them from where you stand. Keep switching your targets, until one of the heads feels the pain and loses HP. When the heads get too close, get away quickly, to avoid their attacks. Their final attack is to regroup into one again, and shoot a mega blast from all mouths. Don't be tricked so easily, because this attack does not take the whole area (be careful when its life is low, because from here on, the Mega Blast does, sometimes, take the whole area). So look for a safe spot in the arena to escape. Then repeat the whole strategy to defeat it.
An alternate strategy is to "hit and run" when Trismagia splits into 3, and keep doing so until he reunites again into a sole head, as even if he attacks with all the 3 elements at once in this phase, it is to note that he also takes more damage while united than when separated. DT-firearms combo will damage Trismagia for considerably more damage.
Afterwards, don't run into the portal immediately. Instead, inspect the chair in the room which will be another secret mission.