Black Obelisk
CommunityCommunity-sourced: based on player reports and not yet verified by this site.
The Black Obelisk is the end-game structure in Big Walk that appears after the four colored towers are finished. It holds the black key tied to the Big Wall achievement.
The Black Obelisk (sometimes called the Black Tower) opens by itself once the Red, Green, Yellow, and Blue Towers are all completed. Community guides report that bringing six blorbs to the obelisk and working through the final section rewards the black key, which is tied to the Big Wall achievement for going beyond the wall. Because the obelisk sits at the very end of Big Walk's progression, details are kept light to avoid heavy spoilers; this page will be expanded with verified solutions.