Defeating Trismagia could be tricky at higher difficulties.
If you intend to earn every trophy in the game, you'll have to fight Trismagia at least FIVE times (not considering the cheat codes allowed in the EUR version of the game). This is what I recommend:
- Dante (Normal)
- Lucia (Normal)
- Dante (Hard)
- Lucia (Hard)
- Trish (Must Die)
Trismagia is a demon whose main form is an enormous head with three faces. Each face represents an element (Fire, Ice and Electricity) and can attack the character separately. The three faces will then recombine to strike a "three elements" powerful attack quite harmful at higher difficulties.
Each character requires a slightly different strategy.
For the moment, I'll give some advice (the best way I found at the time) about defeating the Boss with Dante. Later I'll update the solution with Lucia's and Trish' strategies.
When the faces attack separately, they're more difficult to hit since they move and approach the character to strike the single element attack. Jumping is NOT useful to avoid the attack, so dodge like crazy. During this time, you need to fill the Devil Trigger Gauge (if empty and if you can't or don't want to use Devil Stars).
To do so, try to hit the face with your sword and shot with the firearm you leveled up most (in my opinion the best are Ebony and Ivory or the Shotgun).
After some time, the three faces combine in the single head form that prepares to attack Dante with the three elements attack. Trismagia stays still and quite far from Dante. This is the moment to Devil Trigger and shot the Boss with Ebony and Ivory, The rapid fire will deplete Trismagia's life bar very fast (it depends on the difficulty). Try to avoid the attack then, if the badass is still alive, rinse and repeat the cycle.
After a couple of tries, you should be able to say goodbye to this Boss