The Black Obelisk is the tall black tower your group keeps staring at from across the island long before you can reach it. It is the last gate before the ending, and it trips up more players than anything else in Big Walk. The important thing to understand is that it is a lock, not a dungeon. You cannot force it open early, and once it does open, the job inside is short.
Quick answer: The Black Obelisk door opens by itself once the Red, Green, Yellow, and Blue Towers are all finished. Bring six blorbs to it, and it hands you the Black Key.
Where the Black Obelisk is on the map
The Black Obelisk stands in the middle-western part of the island. You can pick it out on the horizon very early, right from the large open grassy field near the start of the main area. Seeing it is easy. Reaching it in a usable state is what takes time.
Two tools make the trip much shorter. The Map Room flags every puzzle you have already cleared on its 3D island model, so you can see exactly what you still owe. The chairlift, your reward for finishing the Green Tower, cuts out a lot of the walking between the Blue, Yellow, and black towers.
What actually unlocks the black tower
The Black Obelisk door stays shut until the four earlier colored towers are done, no matter how many blorbs you are carrying. Once the last of those four is finished, the door opens on its own. There is no separate switch to hit.
The full chain runs like this: the four colored towers open the black tower, six blorbs inside produce the Black Key, the key opens the Wall, the Wall leads to the long walk, and the giant Sphere holds the real puzzles. Each tower gives you a blorb count to hit and a reward that opens up more of the island.
| Stage | Blorbs needed | What it unlocks |
|---|---|---|
| Starting Area | 4 | Red Drawbridge |
| Red Tower | 5 | Map Room |
| Green Tower | 5 | Chairlift |
| Yellow Tower | 5 | Tunnel system |
| Blue Tower | 5 | Monorail |
| Black Obelisk | 6 | Black Key |
After you feed the obelisk six blorbs, it produces the Black Key. As with the other keys, you carry it through the cutter machines, following the arrow that appears on top of the key to reach each next station until it is finished.
You do not need six purple blorbs
This is the single most common piece of bad information about the black tower. Some players insist the obelisk demands six purple blorbs. It does not. Purple and red blorbs share the same slots and work interchangeably, and plenty of groups filled the obelisk with ordinary blorbs before ever seeing a purple one.
Purple blorbs belong to the post-game challenges on the eastern ridge, which normally open only after you beat the game. Do not go hunting for them before the obelisk. You will only waste time on content that is not gating the black tower.
If your group is stuck, challenges can be skipped
The host can turn on challenge skipping from the accessibility menu when starting a session. If your group is hard stuck and cannot scrape together six blorbs, that is the escape hatch. It exists so no single puzzle can stop you from finishing, including ones that rely on hearing, speaking, quick reactions, or fine motor control. Treat it as an accessibility option, not a shortcut for puzzles that are merely tough.
What is inside the Black Obelisk
Not much, honestly. The obelisk is a key forge and little else. The heavy puzzle content lives later, inside the Sphere, and those are the hard ones because you cannot talk to your teammates while solving them.
There is one strange extra. Some players report that activating the black tower door makes one member of the group see a vision the others do not get. Multiple groups describe the same thing. How the game chooses that player, and what the vision means, is not known, so if it happens to you, nothing is broken.
What comes after the Black Key
Reaching the obelisk does not finish Big Walk, but you are close. House House describe the game as having a beginning, a middle, and an end, and most groups hit that end somewhere around seven to ten hours in. Here is the stretch that is left.
Why the credits are not the end
The first ending is not the finish line, and the game tells you so, which is why so many players go looking for what they missed. Seven purple challenge puzzles open behind a purple door at the far eastern chairlift station. They are harder versions of things you have already done. Clear all seven, plus anything you skipped, to reach the true ending. You do not need every blorb on the island for the first ending, though, because the world holds more than you need.
Achievements tied to the black tower and ending
| Achievement | How it unlocks |
|---|---|
| Big Wall | Pass through the Wall gate after using the Black Key. |
| Big Goodbye | Reach the first ending (secret trophy). |
| Big Game | Finish absolutely everything, including the purple puzzles (secret trophy). |
Only around 1.9% of tracked players hold the platinum, so full completion is rare. There is also a real co-op trap here. Progression trophies unlock when you personally cross, enter, or ride something, not when the group unlocks it. If one player builds the key and passes the Wall while everyone else is elsewhere, the others can miss the trophy. Do these interactions together.
Big Walk supports crossplay, but there is no single-player mode and no matchmaking, so you will need a coordinated group of at least two to reach the obelisk and everything past it. Once the four towers are done and six blorbs are in the slots, the Black Key is yours and the walk to the ending begins.
