Mundus is the final boss of this game which encountered in Mission 22 and 23.
Note: on DMD, Dante Deals 1/3 of Normal damage even in DT.
For Normal and Easy, you are simply going to abuse Devil Stars with the dragon. If your orb route is strong then you should have Full DT Runes start by buying the final Purple Orb.
You will need at least 4 Devil Star for Phase I. 5th is used in Phase II.
Another method for this fight is the energy bullets spam (This is the main strategy in DMD). However, this is diffcult to be consistent at and requires a good luck where mundus would keep exposing his core. Bad RNG would force you to throw another dragon at the end. Another factor for this is how fast you break the Dark Sphere Summon where you must destroy them to break his shield.
Worth noting that with DMD you are allowed to use Turbo which makes your fingers less of a hassle.
When fighting Phase I especially in DMD, you need to be familiar with his patterns. You can't afford to take more damage due to his Phase II. Mundus patterns are split into two categories:
Mundus Phase 2 Untouchable Safe
Mundus Phase 2 Round Trip + Meteor Loop DMD
DMD Round Trip + Meteor Loop is the fastest and best strategy against this boss but, it has big RNG factor whether Mundus decides to break the platform or not. The approach here is to loop until the platform comes closer to Mundus then jump over it to carry on the loop as you pray that Mundus doesn't break it. For the most part, you have to stay right edge, so you could avoid most of his sphere lasers. Roll for iframes when necessary. You will also have to break sphere that is close to you, if Mundus summons it.
If the DT runs out, throw Round Trip then spam taunt to refill the runes and repeat.
If Mundus breaks the platform, then it's highly suggested to quickly equip shotgun. Here are some notable patterns to pay attention to while waiting for the next platform to rise.
Sphere Breaking (1)
Deflect White Fireball (2)
The most important one is dealing with a row of six beige spheres that appears in front of Dante on the outer platform. Run between two of them and fire four shotgun blasts.
(2) This is a very intimidating attack. Anywhere from four big spheres, fireballs will be created and orbit Mundus. After a second or two, Mundus will do a release pose and the fireballs will fly towards Dante.
DT and deflect them back towards Mundus using Dante's short, 3-slash combo or delayed reverse double slash combo.
Standard Vortex Method