TerraDave
5ever, or until 2024
I liked a lot the bits about how a Beholder behaves in combat as a legendary creature.
The main idea, is that legendary creatures can use "legendary actions" to interrupt or alter the normal initiative flaw, giving you a feeling like you are not fighting one isolated monster but a band of eye rays. I guess the added value here (unlike when normally fighting multiple monsters) is that those "legendary actions" can happen at unpredictable initiative counts.
they also note that this is optional...you can fight 4 normal beholders instead (?!)