Pillars of Eternity: Complete Edition

The Hadrian dragon lives on the 15th floor under your fortress (the most powerful creature in the game), the celestial one in the Hailin Temple.
One of the two dragons in Morgek-Yen is also an Hadrian one.

Got the trophy without going through the dungeons in our castle. Completed the entire expansion about the white transition, killing the optional dragon in the ice cave, and also dealt with two dragons in Morgek-Yen. Then he continued the story and killed the dragon on the assignment “nest above the clouds” (given by one of the four gods). The prize was given immediately after killing the quest dragon, by the way it is very light and very easy to stun.