When you catch Calyrex and separate the master and steed, do both natures randomize? I hate nature mints. I prefer the Pokémon to have the actual nature I want on it instead of a cover up.
It will be calyrexes nature as calyrex is the base form this is also with evs and ivs
Source:i had an adamant calyrex and jolly spectrier and when I fused it was adamant