Turn on the animation, and you get a glimpse of all the Ultra Beasts as they descend upon Alola
If this card is destroyed by battle or by card effects, while having Xyz Materials: You can target 1 of the cards used as Xyz Materials, Special Summon it to the field
This basically means you can use any manner of Equipment, buff spells, or anything else you want, to make them as big as possible, and then just do a little bit of light storming in order to finish off tough Creatures or opponents
Regigigas has also given decks like Lugia more tools to combat high-HP Tera Pokmon, while Black Belts Training fixed math on several archetypes to score key knockouts
I mean, come on, the superhero and tabletop gaming universes are so expansive there would only be uproar if a couple of Secret Lair drops or preconstructed theme decks tried to cover everything