"The school I went to had a colony of merpeople, Scottish merrows, in the lake. While I didn't know them well at all, I had a friend who spent a some time down there and passed the information along to me." During the war, they entered into careful negotiations with the merpeople to see if they could find and use an underwater entrance into Hogwarts.

If there is permission to stroke, then Sebastian will indulge. Traditionally, manticores are signs of war to come, but that doesn't bother him in the slightest.