Lux Solis Mirror Challenge
Lux Solis Mirror Challenge is a challenge within the Titan Taskforce Main Quest Line located at the Arena at the Lux Solis Campus. This challenge uses a Reflection Module which will generate a line-up of Coromon that identically matches your own. You will need to win this challenge to be able to progress through the Titan Taskforce Main Quest Line. You will not be able to use items during this challenge.
Strategy
It is ideal to have Coromon in your line-up that have, in its move set, a weakness for the type the Coromon is assigned; for example: Serpike, being normal type, is weak to poison type moves, therefore having poison moves would help Serpike beat a Serpike. This is so you don't have to change Coromon during a battle. Serpike also has the Super Drain move, which will allow it to heal itself with the damage it caused the other Coromon, this is not unique to Serpike, so there are other options of course and this move is advantageous since you cannot use items during the challenge.
Another thing to consider are the other moves you allow the challenger to use, If you provide weaker moves or moves that do no initial damage the challenger may use those moves instead of the stronger moves giving you an advantage.