The Rot-Behemoth

Ecology
The Rot-Behemoth is a massive, multi-headed siege beast formed from the fused, necrotic remains of woodland creatures and corrupted roots. Animated by the Emerald Rot and directed by Xylira’s hive-mind, it serves as a living battering ram for the corrupted Sylvan Elves. It is a slow-moving mountain of moss, bone, and pulsing green spores.
Combat Mechanics
The Rot-Behemoth is a juggernaut of destruction. It features multiple "Head" attacks (representing the various creatures fused into its mass) and can exhale a 30-foot cone of concentrated Rot-spores that poison and decay everything they touch. It has the "Siege Monster" trait, allowing it to deal double damage to objects and structures. Its sheer size makes it difficult to distract, and it is immune to the charmed and frightened conditions.
Loot
The core of the beast contains "Corrupted Heart-Wood." If purified through a lengthy alchemical process, this wood can be used to forge powerful nature-based staves or bows that grant the wielder limited control over the forest.