Solterra honestly, and possibly obviously, is neutral to everyone until they make an attempt against him, his people, or his friends, for no good reason(s). So, his people will not attack yours unless their lives are threatened, it's what they've all been instructed to do. Though, I am curious as to the plans of Grindan's as of late. Did you know Solterra is marching to Rone's Fortress in full force?

^ This is not a spoiler. To those that don't know it will be painfully obvious once Flooby has the time for a joint collab

Edit: Also on that note; everyone can consider Dread to be a totally separate character from Solterra, and would never even attempt to ban alcohol, just as one example. He is a bit gritty, though.