Challenge Mode gives players a chance to earn extra rewards from a raid boss by fulfilling a set of hidden requirements. Each week, the bonus opportunity shifts to the next boss in line. There are three Challenge bosses in Wrath of the Machine, and Vosik is the first one up.
While Challenge Mode requirements are a puzzle that must be solved, they're also set for each. You might know how it's done, but the execution is the tricky part.
I successfully ran through the Vosik challenge on Heroic Mode a few hours after it launched, so I figured I'd spend some time telling you how it's done and offering some tips to minimize your frustration.
Whichever difficulty you plan to tackle Challenge Mode on, make sure your fireteam is raid-ready. For normal mode, that means you'll want everyone to be at or above Light 370; for heroic, make sure you're all at or above 390.
That's not to say this can't be done with under-leveled Guardians. But completing the Vosik challenge hinges on a mixture of enemy crowd control and fast, efficient boss DPS (damage per second). Under-leveled players do less damage and take more, and someone will have to pick up that slack.
Beyond that, it helps to have at least one Defender Titan with a Weapons of Light bubble to use during the DPS phase. It's also smart to bring along at least one or two Nightstalker Hunters. Their invisibility smoke makes it easier to grab bombs on Vosik's side of the room and their tethers amp up damage even further during the DPS.
That's all you really need. The Outbreak Prime exotic pulse rifle deals very high damage to Vosik. Swords — particularly void swords — or Gjallarhorn are best for dealing with the Captain Majors that spawn throughout the fight. Ultimately, go with the loadout that works best for your while optimizing your Light.
How the challenge works
I'm assuming that anyone who's going after the Vosik challenge is already familiar with the basic mechanics of the fight. Here's a great video explanation of the fight (starts at around the five-minute mark), but if you haven't beaten Vosik the "normal" way, do that first.
So. Challenge Mode. There are three key elements to earning Vosik's bonus rewards:
You must complete the fight in three damage phases — no more, no less
After each of the first two damage phases, you must use both of the safe rooms that light up
During the two safe room phases, you must activate both doors using the two SIVA bombs that drop during the damage phase
It doesn't matter how many people go into each safe room; you just need to make sure the bomb carriers are split up. It helps to designate your safe room bomb carriers before the fight starts; once the bombs drop during the damage phase, their sole priority should be on spotting the rooms they're running to and shouting them out.
Usually you'll have one safe room lit up on each side of the room after the damage phase, but that's not always the case. The whole fireteam should be ready to run to the left or right side of the room if that's how things shake out.
Bomb carriers should take note: your bomb's splash damage won't have any effect on the door controls. When you toss the bomb to lock up a safe room, make sure you're aiming directly for the flashing circle that you would normally shoot during a non-Challenge version of the encounter.
Communication is key here. Your bomb carriers should try to avoid talking over one another when calling out the safe rooms, and they should be the only ones talking in that moment. Everyone else should be listening carefully for direction while focusing on DPS.
That's all for the Vosik challenge. Everything else in the fight works as it normally does. The trickiest thing for a lot of groups will be finishing the boss off in three damage phases. Everyone should make sure to use the Weapons bubble. And if you have at least two Nightstalkers, make sure they space out their Supers so Vosik is tethered for the full length of the DPS phase.