[Mechanic] HoloDisplays countdown timer for bossmob spawn

Croderai posted a question here.. it caught my imagination, so I tried to make this mob (as I had a little time).. but unfortunately, HolographicDisplays doesn't allow anyone other than a player run the commands to create or move holograms.

The only way I got it to 'work' was to have a hologram in a set location and then the 'UpdateTimer' mob updates it before summoning...

[Mechanic] HoloDisplays countdown timer for bossmob spawn