During the Dragonflight 10.1 Embers of Neltharion questline, you could complete two separate questlines focused on Alexstrasza and Kalecgos.

A Blue Dawn Questline – Kalecgos tasks his dragonflight to bring the remains of various deceased Blue Dragons to the Ossuary in Thaldraszus. Then sends you around the world in search of Blue Dragons that didn’t answer the call to return to the Dragon Isles.