Here is the full list of all 40 Arkane Rush Multiverse Mayhem achievements.
Defeat 5 Goblins
Defeat 5 Armadillos
Defeat 5 Beholders
Defeat 5 Imps
Defeat 5 Ents
Defeat 5 Golens
Defeat 5 Necromancers
Defeat 5 Wolves
Defeat 4 Orcs
Defeat 5 Foxes
Defeat 10 Red Imps
Defeat 3 Red Necromancers
Defeat 7 Orcs
Defeat 10 Ents
Defeat 8 Golens
Defeat 20 enemies
Defeat 50 enemies
Defeat 80 enemies
Defeat 110 enemies
Defeat 140 enemies
Defeat 170 enemies
Defeat 200 enemies
Enter the portal 1 time
Enter the portal 2 times
Enter the portal 3 times
Score 200 points
Score 400 points
Score 600 points
Score 800 points
Score 1000 points
Defeat a Wolf with 3x Combo
Defeat a Fox with 3x Combo
Defeat an Ent with 3x Combo
Defeat a Golem with 3x Combo
Defeat an Orc with 3x Combo
Score 1200 points
Score 1400 points
Score 1600 points
Score 1800 points
Score 2000 points