Not much is known about Cailan since he went missing during the move from the Crystalpine Reaches. In fact, only Candace is convinced he is even still alive.
Cailan first met Candace not long after she arrived to the Crystalpine Reaches. The two hit it off immediately and decided to share a lair, eventually leading to a large family. With a few other dragons their home was no longer big enough to comfortably fit everyone, so they decided to move to the Starwood Strand. Candace was worried about the rumors of dragons becoming lost there and if they would be able to protect their family as well in the forest, but Cailan was able to convince her everything would be fine. Unfortunately, he was wrong.
Once Cailain and Candace packed up the lair and made sure everybody was ready to go, the whole family flew together as a group to find their new home. A perfect clearing was found, but before building was completed Cailan was suddenly not there. A couple of dragons were convinced he had gone scavenging, maybe hunting, or even fishing (none knew exactly), but after a few days passed it was clear he wasn't coming back.