Welcome to my rather verbose guide for completing the new Curse of Osiris heroic strike; the ‘Tree of Probabilities’. Both the written piece and video guide are focused on the most efficient route for completing the strike. Barring minor alterations (or possibly, yet uncovered glitches), this is currently the fastest way to complete the strike. Hopefully then, the video and written guide will arm you with the information you need to expediently farm the strike or complete it without any major inconveniences. Additionally, this guide should be still be valid when the strike gets placed into the Nightfall rotation, when speed becomes required for completion. I will endeavour to update if it is not.
The ‘Tree of Probabilities’ heroic strike is actually just the story mission that goes by the same name, but for three people, tougher and with some minor alterations mixed in. Put another way; more majors, higher Light level requirement and more enemies. So if you can recall the ‘Tree of Probabilities’ story mission, you should already have a good understanding of what needs to be done.
The video is there for people who want something a bit quicker to digest, but lighter on details. The written guide is for those that enjoy a deep dive into the strike’s details, characteristics, quirks and all that comes with it.
You spawn in the Mercury overworld at the foot of The Lighthouse. Like every strike, story mission or adventure set on Mercury, you need to head to the giant blue triangle portal that takes you to the Infinite Forest. It’s on the opposite side of the Mercury map directly ahead (just run around the giant circle in the middle), there will be enemies in the area, but you can safely ignore them and just blaze past them.
Once you get close enough to see the portal however, you’ll notice that it’s red instead of the typical blue. The Cabal have set-up a forcefield that bars the way. Two dropships will fly in and drop some Cabal off (roughly six, sometimes more, consisting of a few legionnaires and an Honoured Colossus), you need to kill those particular Cabal for the shield to deactivate. Once you do, head through and follow the big triangle tunnel to the next section, the ‘Infinite Forest’.
The Infinite Forest
Lego Infinite Forest is Bungie’s attempt at making random terrain. Besides a few set pieces (namely the first and last), every piece between those two is variable. It is important to note, that the pieces themselves are not random (they’re prefabricated), but the order they appear in and how they connect changes. So basically, Lego pieces. Thus, it’s somewhat difficult to give exact directions on how to navigate the Infinite Forest.
Both of the new Curse of Osiris strikes (Tree of Probabilities and A Garden World) share the Infinite Forest segment. The difference between the two is the length; with Tree of Probabilities’ Infinite Forest segment being about twice as long to compensate for its shorter final section.
With all that being said, there is some general advice that will see you through any permutation of platforms with relative ease.
1. Avoid combat. No enemies possess a trigger that prevents you from spawning in the next platforming section. That is to say, there are no Daemon’s (the enemies that make the doors unusable) that were present in the earlier Infinite Forest content. Protracted battles serve no purpose but to slow you down. There is one exception to this rule, explained below.
2. Follow the twin parallel glowing white beams. Every random platform ends in a ‘door’ (their word, not mine) you must use. These doors emit two parallel white beams of light into the sky, use these to guide you to them. This lets you take some very expedient shortcuts if you know where to go. Sometimes the beams can be obscured by the terrain, if you don’t know where the door would be (it becomes more clear how the pieces fit together after doing it enough), try to gain altitude to help you spot it. Finally, there is a single white beam that is shooting into the sky, this is where you ultimately want to end up (the triangle portal), not where the next door is, try not to get baited by it like I do.
3. Avoid following the waymarker. Generally the speaking the waymarker tries to guide you through ‘checkpoints’, which are, on occasion, in multiples per platform segment. Usually, this sends you a meandering and inefficient path, only follow these if you get lost.
4. Don’t touch new platforms as they’re spawning in. Seriously, it’s an instant kill if you touch them at the wrong time. Too early and dead.
In summary, just parkour your way to the twin white beams of light and avoid fighting, this yields the fastest path through the Infinite Forest.
As mentioned above, you will need fight some Cabal once you reach the triangle portal to deactivate the red barrier they’ve put in place. The terrain is always the same with a spiral staircase near the portal that leads up to the top, where most of the Cabal are congregating. The quickest way to approach this situation is to just rush to the top and kill the Cabal up there. Any stragglers that jumped down to the bottom will follow you back up so you don’t need to chase them around. Once the barrier deactivates, head through the portal and progress down the giant triangle tunnel to the final section; ‘The Rack Track’ (I dunno, couldn’t come up with a better name).
The Race Track
After coming out of the portal, run straight ahead and you’ll see a hefty assembly of enemies in front of you. Thin the herd out until your Ghost allows you to mount your Sparrow and do your best Blues Brothers impression over the gap that the enemies were fussing over. Ride your bike towards the giant pipe on the left and just follow the path (avoid the rotating laser beam, or not, up to you) around. You’ll eventually come to a fork in the road, a path to the left, right or centre. Technically speaking they’re all the same road, just on different elevations and sporting slightly different obstacles. but once you commit you can’t change unless you drop down into the centre where the enemies are. Personally, I find the right most path safest; no enemies, the most stable ‘road’ and the most easily navigated laser sets. Just ride the course to the end.
After the final jump, you’ll be forced to dismount your Sparrow as it can’t climb 90 degree cliffs like the superior ME1 Mako can (and you lose the ability to resummon it). Scale the small ledges and head right. You will see a large amount of Legionnaires/Goblins and Psions/Hobgoblins along the path, all keen for your head (but none with the ability to aim for said head, poor dudes). Do what every Guardian with places to be does, run. A straight sprint to the end of the path is the easiest and fastest method for getting to the boss. The path will end and you’ll see a large opening in the left wall, head through and into the boss room.
The Boss Battle – Walkthrough
Kill all the enemies in the room, an ultra Minotaur will spawn in the centre, but is immune – don’t waste ammo on it. Very shortly after, Valus Thuun will give you his best wrestling impression from the ledges high above and destroy the Minotaur. He is momentarily immune while performing his top-rope antics and shortly thereafter, so keep your finger off the trigger a bit longer.
Once he’s vulnerable go ham. Be mindful of the mechanics listed in the section below and don’t forget about the lasers. Once Thuun has endured enough damage (about ⅔ HP remaining), he’ll retreat back to a room and a mixed wave of adds (additional enemies) will enter. You only need to kill the Minotaur to progress, as killing it will drop the white shields blocking the circular cut-outs in the wall you to pass through to enter the next area. Killing all the others enemies for ammo isn’t a bad idea, but hardly necessary as far as the fight is concerned.
You’ll need to run through to the next room (avoid the lasers) in which the cycle repeats itself. The lasers are positioned differently and the room geometry is different, but you just need to repeat the steps from the first room to force him back again. He retreats at about ½ HP.
You’ll need to run to the final room, doing a simple platforming challenge as you go (don’t nearly die in the name of saving a second like I did). The cycle once again repeats itself, with different laser placement and terrain. The only real difference is Legionnaires will spawn in to help Thuun more frequently (but not in overwhelming amounts), and you can fall off the far sides of the arena. Thuun won’t retreat from this room and will fight to the death; oblige him and collect your loot.
The Boss Battle – Mechanics
These are all the mechanics involved in the fight (basically all the things that try to kill you). Thuun’s weak-point is the same as every Cabal, his head and the more effective but harder to reach; back vent. Valus Thuun himself doesn’t have very many mechanics, listed out, they are:
1. Firing his gun. I mean, he just fires his gun at you. It’s a projectile minigun style weapon that fires relatively fast, but due to it being a projectile with a small hitbox and the AI always aiming for your centre chest at the point of firing (i.e. they don’t lead, how did the Red Legion never lose again?), simply strafing in a direction avoids it. Cabal military training at its finest.
2. Standard radial knockback based on proximity. Get too close and he’ll use it. Knowing this you can manipulate his move-set somewhat. It’s a lengthy animation and he won’t commit to any other action while performing it. Getting hit into a wall at high enough speed (or flung into the abyss) and you’ll be waiting for a revive though, so exercise caution.
3. A downwards charging slam with knockback. Thuun will momentarily hover in the air then fly at his chosen target’s position in a straight downwards line with his arm out (think Superman, but with one arm). When he reaches his destination (basically where his target was standing when he initiated the move) he’ll do the standard radial knockback effect. This is essentially the knockback above with a telegraphed charge tacked on.
4. Charges up, then fires his gun. This move is legitimately dangerous and if he catches you unaware with it, you’re gonna have a bad time. Unlike the normal firing of his weapon, the hitbox for these projectiles are massive, about the size of a typical Colossus firing his main weapon. Just imagine a Colossus firing his cannon about three times faster and you have a pretty good idea why this will own you. Again, it’s a projectile and dodgeable, but due to its size and damage, it’s less forgiving. Additionally if the projectile clips you, it’ll knock you to the side without about the same strength as his other knockbacks. This can be super dangerous in the last arena as you can be flung off the map. Use the charge up time to establish either a fast perpendicular movement pattern to his firing line (jumping works well if you have a fast jump), or just hide.
There are two more mechanics pertinent to the fight, but neither belong to Thuun. Each stage of the arena has little brown squares with red lights in their centre, these are scattered about on the walls. These doodads emit the red laser beams you seen earlier in the strike during the Sparrow section. They light up in patterns that change semi-frequently. However, the lasers are not very smart, as they telegraph their intent. The beam will glow orange first, turn red, stay red for a time, then back to orange before turning off completely. Orange beams don’t deal damage, the only purpose they serve is to let you know the beam is either going to turn on or off. The mechanic is quite easy to navigate with a bit of situational awareness. If you stumble into a red beam you will take a lot of damage however, most likely dying unless your contact is fleeting.
The final mechanic is adds (additional enemies). Besides the first set of enemies you need to kill to spawn Thuun and the final area, adds spawn in very small amounts, which is a nice change of pace. Most of them spawn when Thuun retreats to the next area. Usually a mixture of Legionnaires and Harpies will flood in and begin exchanging blows around a single ultra Minotaur. The Minotaur needs to die to progress to the next room, so you can ignore the other adds if you so choose. The final part of the boss will have Legionnaires spawn in greater numbers than before to support Thuun. That’s about it regarding the way the boss tries to have you slain, fairly straightforward for the most part.
Ultimately, the strike is fairly quick and easy as long as you aren’t compelled by the urge to commit genocide. If you engage in every battle, you’ll likely double the length of the strike. The enemies aren’t threatening enough to stop you from sprinting through and there is so much terrain blocking line of sight that they struggle to hit you anyway. The boss fight itself is a bit of a pushover especially when you compare it something like Savathûn (man screw that guy). I personally expect the Nightfall versions of the new DLC strikes to be absolute pushovers when compared to Destiny 2’s vanilla strikes.