>>19989523Regigigas.
1. It's a cool trio master, and acts as a nice little bonus for collecting all three Regis.
2. It's got it's own unique move.
3. It's got a cool backstory.
4. It actually makes some kind of sense in being it's own unique creature, unlike Keldeo who's just it's own species because >muh 3 musketeers reference
5. It's found in ruins, which are pretty neat.
