Please, write here only clues you had and you resolved. Do not ask for answers. Let's make this place clean. Lvl 3 Laugh in the Jokul's tent in the Mountain Camp. Beware of double agents! Equip a rune full helmet, blue dragonhide chaps and a fire blattlestaff. Show Laugh emote in tent with Muddy Rock inside. Mountain Camp is part of Mountain Daughter Quest, and you have to at least start it. After showing the emote lvl 108 Double Agent will attack you, he fight with melee and doesn't poison you like Saradomin Wizard always do. After you kill the Double Agent, repeat the emote and Uli, second double agent will show and give you the casket.