An extremely lucky player received both mounts from Malygos in a single run.
Reddit user Daniel_545 got extremely lucky and received both mounts from Malygos in the Eye of Eternity in a single run. Reins of the Blue Drake has an approximately 5% chance to drop and Reins of the Azure Drake has an ever lower chance to be found in the cache that spawns after Malygos is defeated. Seeing both drop at the same time means you’ve used up all your luck for the rest of the expansion.