With regards to the Revenant universe that caused Portia's death, both Dante and Portia pretended like they did not exist for now. They allowed them to grind down Dante's troops and provide them with field training, but neither of the two who could likely wipe out the entire universe made a move.
After all, they had other things to focus on right now, and they wanted to deal with those fellows slowly and methodically, carving out their flesh inch by inch while they screamed in agony. When that time came, the Revenant Universe would pray for a quick death.
As for Dante's Martial Artist Army, it was something inspired by Beatrice again. After settling down with Antonia in the First Gate, Dante finally managed to pressure Beatrice to accept the Heavenly Scroll of Infinite Paths, which would awaken her latent Internal and External Arts abilities in reality.