Rampart fiend
Rampart fiend is one of Deopa's creatures: a shape that belongs to the Deep that Deopa, the Deep holds within himself. It is not one of the natives' dead. Its affinity is Umbra, and a mage whose core woke in that affinity casts its calling with the grain.
No barracks trains it. It comes into a kingdom only when a mage casts Summon rampart fiend. The Deep's bargains consume people, so every turn it stays, the kingdom pays in its own folk as well as in the mana that holds the called shape. Once struck, the bargain cannot be dismissed. No order sends it back, and no shortage in the kingdom breaks it loose.
The Sealborn who have fought beside it call it a wall that walks. They say the Deep shaped it to guard: it carries a great shield, holds riders off at a long reach, and is still standing when a long battle has worn lesser troops down.