When you arrive you should encounter some Blood Goats waiting for you. Get rid of them to move on into the elevator full of Agonofinis so this place is a great way to boost your Stylish Rank. Once you exit move down towards the screen and break the vase which uncovers the final Secret Room. Now continue back on the path until you reach the disfigured room that seals you in with Jomothumsira that will reveal a Sacrilege when you defeat them. Return back using the Sacrilege and continue to move on straight where you’ll encounter the floating pink orbs. Just hop onto the upper level collect the Sacrilege and make sure to go to the other side of the level to get the final Blue Orb Fragment. Again, return back through the door and once you reach the hallway to the next room turn right through the narrow path.
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.