On Xagobah, the Mazariyan stood as a Separatist stronghold. The Techno Union engineered this citadel to be the personal domain of Wat Tambor. Its construction involved a unique blend of advanced Techno Union technology and native bioengineered fungal organisms, resulting in a structure that was essentially a living being. Wat Tambor corrupted Xagobah's natural fungal life, transforming harmless, bacteria-eating fungi into bloodthirsty abominations. The citadel's exterior resembled a somber, black step pyramid, reminiscent of those on Yavin 4. Its sleek surface throbbed with life, and lightning bolts coursed along its sides. Protruding from its surface were elongated, black spines that could extend and retract, impaling any intruders who ventured too close. Droids and cannon emplacements lined its battlements for defense. The fortress's entrance was a large, triangular opening at its base, capable of unleashing thousands of droids onto the battlefield. Ringed fungus blades and long spines jutted from the ground, surrounding the entrance. The Mazariyan's interior was a hybrid of organic and inorganic elements. Luminous mushrooms, bioengineered to integrate with metal and plasteel circuitry, illuminated its fungus-covered metal halls. Nanotechnology and biological circuits merged computer intelligence with the semi-sentience of the bioengineered fungus that formed the fortress. Microscopic nanotechs instantly repaired any cracks or fissures caused by external attacks. Numerous chambers branched off from the main hall and staircase, including one containing Xamster and clone prisoners trapped within fleshy walls, struggling as the living fortress consumed their fluids. Another chamber resembled the interior of a Human heart, pulsing rhythmically. Deeper within the fortress, Xabar fungus grew from the walls, paralyzing intruders with neurotoxins emitted from its tendrils. The fortress's core was a vast chamber, more akin to a cavern. Circuits and monitors covered the area. A massive, shapeless purple mass pulsed and shuddered from the floor, resembling a giant slime mold. Dozens of tentacle-like tubes pulsed with a darkly glowing violet liquid, flowing outwards into the walls. Other veins, rippling with a deep red color, siphoned bodily fluids from captured intruders, directing them into the bioengineered nerve center to nourish the organic construct. This explained why many who entered the Mazariyan never returned; it devoured them to sustain itself. Boba Fett was among the few who escaped the Mazariyan in 19 BBY. Discarded bodies were incinerated in a separate chamber. Below the fortress were vast storage areas containing the thousands of droids used for its defense.
During the Outer Rim Sieges of the Clone Wars, the Galactic Republic besieged the fortress. Republic forces concentrated their assault on the main entrance, establishing a strong foothold in front of it. Unable to penetrate the fortress's self-healing walls, the attacking generals dispatched several ARC troopers to infiltrate the citadel. However, the fortress's biological security systems inevitably detected and incapacitated these troopers, who were then fed to the Mazariyan. After weeks of relentless attacks, the fortress eventually succumbed when it exhausted its droid forces and sustained more damage than its nanotechs could repair.