The Legendary/Mythical Crate on our All The Mons server contains 10 Legendary and 5 Mythical Pokemon, as well as their shiny varient. 

Every 1-2 weeks the Pokemon in the crate is randomised. 

You can view the potential Pokemon in the #development-updates-atmons channel on discord or by left clicking the crate in game.

Each player is limited to 1 Legendary/Mythical Key per month.