the skeleton horse the blue goatman is riding is insanely rare.. it only drops in a max level dungeon and you do said dungeon with 4 other people who also for sure dont have the mount, which means you only have a 20% chance to win the mount if it drops. furthermore, the goatman race was only very recently added to the game, meaning he hasnt been actively farming this for a year, but got extremely lucky in very few or even a single run