It's an alright early game Pokémon, but it might be smart to switch it out for an Absol in Fortree. I used a Mightyena to go through the E4, but it could have been a lot easier if I had a stronger Pokémon (like Absol, for example) in that slot. A strong ghost type Like Gengar can also be useful if you want a good Dark move user. Ghost Pokémon are generally pretty helpful late game, especially in the Gen III elite 4.