Forest Boss Chests are items that can be obtained by defeating the Ghastly Tree boss that can appear in The Forest. It, like other Main Hub boss chests, can drop gems, crate keys, hoverboards and a pet. Forest Boss Chests cannot be burned at the Incinerator in the Junkyard.
As of v1.103.0, this item can be converted by the Main Hub Gumball Machine into Gum. The exchange rate is 1:1.