A gated rail portal admitting compatible trains and key holders into a vast zombie-infested switching and repair yard.
Carl stops the Nightmare Express before the portal and confirms that his engineer key and compatible conveyance authorize passage. Unlike the abyss portals, it is two-way and the track continues through its swirling threshold.
On the far side, automated switches control a root system of diverging rails. A short red steam train exits while Carl watches, and his screenshot reveals a massive yard still filled with zombies, including an infected Cornet.
A huge swirling gateway pierced by working rail tracks, opening onto a root-like junction of many lines in a zombie-filled train yard.
The portal is the party's only controlled path onward and leads directly into the dangerous repair complex.