Destiny 2 Curse of Osiris Tree of Probabilities Quest
Now that we know where the Infinite Tree map is located, it is time to make some headway in dealing with the Vex threat. Return to Mercury and approach the quest marker for the Tree of Probabilities. This mission involves heading into the Infinite Forest once again, so be ready to fight. I won’t be covering anything to do with the Infinite Forest in this post as other posts (like this one), cover the general idea of the area (it doesn’t change much as you playthrough the story).
Start the Tree of Probabilities Quest
When you are ready, head to Mercury and make your way to the start of quest flag located at the base of The Lighthouse. Activate the quest and get ready to fight a ton of Cabal.
Fight Through the Cabal & Enter The Infinite Forest
As soons as you begin the Tree of Probabilities, a number of Cabal will overrun the area between you and The Gateway. Fight your way through the Cabal and enter the Infinite Forest. From here you will need to make your way through a number of Infinite Forest sequences to reach the next tower. Before you can access the tower, you need to break the barrier. This basically means to kill all the Cabal around you. Clear the area and make you way inside the tower. Here you will find a portal to a Cabal attack simulation, head through it.
Cabal Attack Simulation
As soon as you enter the Cabal simulation, you will need to clear the near area of Cabal. There are quite a few Cabal around, so use your special if needed. Once the area is clear, mount your trusty Sparrow and jump the gap in the second picture. After the jump, stay on your Sparrow and ignore most of the enemies here. Continue along the path in pictures 3, 4 + 5 and you will eventually arrive in an area where you need to dismount (Atlas Grove area).
Once in this area the Cabal will launch a full on attack in an attempt to stop you from reaching the map. Fight your way through the Cabal until you reach the inside of the building. Hope you are ready for a boss fight.
The entire third portion of this level is devoted to the boss fight against Valus Thuun. Fighting Valuus Thuun takes place across three phases. Each phase is similar, but the rooms you fight in are different. You’re gonna want to go into this fight with power ammo and your super.
Phase 1: In phase one you will fight in the building entrance. Valus Thuun will attack you straight up and adds will enter the battle. Eventually lasers will trigger that deal damage to you and act as hazards around the room. Once you deal enough damage to Thuun, he will leave the battle and a Yellow Minotaur will take his place. Defeat all enemies to head to into the next room to start phase 2.
Phase 2: Phase two works exactly like phase 1, but the room is larger and there are more adds. The phase will begin with Thuun attacking you and then adds and lasers will trigger as you deal damage to him. Again once you deal enough damage to Thuun he will leave the fight and you will face another Yellow Minotaur. Take out the Minotaur and head into the next room (you will do some minor platforming to get here) for the third and final phase.
Phase 3: I wish I could tell you that Bungie really got weird with phase 3, but that would be a lie. You will face the exact same threats as you did in phases 1 and 2, but you can now kill Thuun. Defeating Thuun will allow you to access the map and complete the level.
After defeating the Thuun, head through the doorway that opens (was locked during battle), and make your way up to the Map. Interact with the Map to learn that we need more processing power, and to trigger the end of the level. The Vex have the processing power, so we will be heading to Nessus next.