Rauru + Sonia concept art

From the official artbook. It's pretty much how they appear in-game, but holy sh*t some of those proposed size differences tiptoe into Skitty+Wailord territory. I know he's pretty tall in-game already, but look at the second pic for example - his head alone is as big as her entire torso. Standing next to him she'd barely reach up to his waist.