Toruga is found in Vlamma, inside Mount Muspel. He only spawns in one location, but fortunately his spawn rate is significantly higher than Nibblegar's and Cubzero's. His exact location is Below 3 which is the final stop before Below 4.
This is the area immediately before the Fire Titan battle.
Save your game immediately, then use a Potent Scent! This will increase your chances of finding a Toruga with high potential. Remember, you just need to find one with a potential of 20 to get a perfect one via the NPC in the Trainer Hub.
Saving the game prior to using the Potent Scent will allow you to restart the game and not waste a scent if you don't locate the perfect Coromon.
With your scent sprayed, you should eventually encounter a Toruga. He will evolve into Embaval at 18, then finally Volcadon at level 36.
Volcadon has a high special attack stat and powerful fire moves, so it functions well as a sweeper. It's movepool is somewhat limited on the special side, unlike Megalobite's, so it lacks moves to check many of it's counters.
This set functions as a mixed attacker as it has both physical and special attacks to give Volcadon some coverage. Body Blast carries a 20% chance to knock down the opponent and can be helpful against specially defensive Coromon.