However because they have a set rotation, you can manually determine the current boss by creating an indexed array and doing a quick modular calculation by getting the number of weeks since they went live. I'll post some code once I get a chance. [edit] Here's an example for determining the King's Fall Challenge in JavaScript. Note the below uses the skulls returned from the ActivityDefinition of King's Falls and filters out skulls that aren't currently active, meaning it also works for Hard mode. [quote]var skulls = tierActivity.skulls; if (activityAdvisor.raidActivities.raidIdentifier == 'RAID_TAKEN_KING') { //console.log(activityAdvisor.raidActivities); var releaseDate = Math.floor(new Date('2015-12-01T09:00:00Z').getTime()/1000/60/60/24); var expireDate = Math.floor(new Date(activityAdvisor.raidActivities.expirationDate).getTime()/1000/60/60/24); var diffDate = (expireDate-7-releaseDate) * 7 + 3; var tmp = []; var offset = 0; if (skulls.length == 4) { tmp.push(skulls[0]); offset++; } var skullIndex = ((diffDate+2) % 3)+offset; tmp.push(skulls[skullIndex]); skulls = tmp; }[/quote] I haven't written one for Court of Oryx yet, but the same logic applies. Figure out the rotation order and the first reset after TTK came out (bungie time) and then determine how many weeks have passed since then and % it to get your skull/boss index. It's a little bit of work, but worth it if you want to display this on checklists etc.