You know there are names there I don't even know? XD Got some background research to do as I'm barely familiar with the legendaries post Kalos, but sure. 

Your Heatran has a quiet nature, but I'm going to play him a bit grumpy. When I look at him I just see a grumpy Pokémon. And I like playing grumpy characters XD 

And I was thinking that if I take Calyrex that you could take both Glastier and Spectier.

"Zarude are social and live in packs. They're usually incredibly aggressive, and frighten most other Pokémon; excelling in battle with their sharp claws and quick wit."
Sound like Mankey. I think Bear will make a Mythical friend ^_^ Or rival...

Since you play a few full sets, like the kanto and galarian bird siblings, maybe I can take a full set too. The Forces of Nature or the Swords of Justice perhaps?

Also, are there any characteristics of the legendaries that I'll be playing that I have to keep in mind? They are your babies and I want to do them justice. 

I'm looking forward to play Jirachi, that's my favourite legendary. And I have plans for Ho-Oh...
In my own writing I had picked Ho-oh as the special Legendary for Michael, his Cyndaquil and his father, so this is perfect.