Envoys are a bi-hourly event that happens on CYT that anyone can take part in when they've active and last for X minutes.
Typing /warp envoys in-game warps you to the Envoy map. Once an Envoy event is active, 50 envoys (froglights) will spawn throughout the Envoy map, allowing them to be hit to be obtained by players. There are three rarities of Envoy crates, Common, Rare and Legendary, each with a range of prizes that can be won.
Though beware, scattered throughout the Envoy map is a variety of custom mobs, challenging, fast and ever-so dangerous. Be sure to maneuver your way around them if you want to succeed in finding all the Envoys available within the time limit.