Oaken defender

An oaken defender was a rare and enormous plant creature that was the embodiment of nature's rage, arising to defend the sacred groves of dryads when they came under threat.

Description
After emerging from the soil, it had the form of a gigantic slab of plant matter with a roughly saucer-shaped body usually reaching in diameter and a mass of. Its body was like wood, similar to an exposed root, but was usually encrusted with soil and vegetation, making it seem like nothing less than the earth itself come to life. Its body bristled with sharp spikes, as long as small spears and it had six flexible branch-like tendrils emerging it from it at regular intervals, which would be used as arms or legs as needed. On its upper surface, it displayed a sort of wooden face, vast and wrathful. The eyes were bulges sensitive to both light and heat, allowing it to sense its surroundings as well as any, and its mouth was a jagged crack more than capable of devouring its foes.

A buried oaken defender was marked only by a 'faerie ring' of mushrooms around part of the grove. These were not mushrooms at all, but growths on the tendrils poking above ground

Personality
An oaken defender was in fact a peaceable being who thought of itself as a living bulwark in the defense of the wilds. Yet they were supremely confident and without mercy in that defense, and attacked as the dryads required. While the majority were good by nature, some were more neutral, and a few that served corrupted dryads were quite evil.

Although solitary by nature, they were closely linked with the dryads and their grove. This was both a physical link, as they were sustained by those they defended, and a spiritual link, owing to their emotional and psychic bonds. Moreover, although they spent most of their time asleep and were so far apart, they had a kind of dream link with other defenders, wherever they were, so they had a subconscious awareness of each other's feelings and concerns. Otherwise, they had little in the way of community with one another.

An oaken defender had no name, but when needed, it adopted a title based on its locale and the dryads it guarded. One that lived in a grove by lake that was home to two dryads could be called Twin Sisters Shore, for example.

Activities
For nearly the entirety of its existence, an oaken defender slumbered just below the ground of a grove that was home to a dryad, while grass and bushes grew over it and shrouded its spikes. Nevertheless, it was constantly in empathic contact with the dryad, so it could immediately act in her defense against hostile trespassers, and holding back only when mollified by the dryad or another fey being. Afterward, it quickly returned to the earth and its long rest. Hence, they were only ever seen when fiercely defending a grove.

The oaken defender would be aided by the dryad, and potentially by treants and other forest defenders if any happened to be nearby. Militant dryads would provoke conflicts with innocent travelers near their groves, knowing the defender would join their side regardless.

Abilities
It had all the traits and immunities of a plant creature, was highly robust and resilient, and was resistant to attacks from non-magical weapons. It could burrow through the ground, however, slowly, and was well-hidden from sight once it was settled in the earth. With low-light vision and darkvision and tremorsense to, little escaped its notice.

An oaken defender possessed an empathic link with the dryads that belonged to its grove. Though this, it could sense what they felt and needed. This link worked up to away.

Moreover, an oaken defender could sense the location of another of its kind, anywhere on the same plane, similar to a discern location spell. This worked at all times and they were all familiar with another, at least so far as this power was concerned.

Combat
As soon as the dryad or its grove was threatened, the oaken defender burst out of the ground and undergrowth to attack trespassers, waiting only for the majority of them to come in reach of its tendrils. They fought without mercy and according to the dryad's needs in the battle.

In combat, it slammed targets with its tendrils and gored them with its spikes. When facing one or two foes, it moved on four limbs and walloped with the other two, while when facing many foes, it stayed in place and whirled around at all of them. It made good use of its incredible strength and enormous size, striking with the greatest force and cleaving through the ranks of its opponents.

Ecology
Just like the dryads, oaken defenders dwelled in temperate forest environments.

While it slumbered, an oaken defender absorbed nutrients via its tendrils, which sprouted mushroom-like growths on the ends and protrude above the ground to collect rainwater. Moreover, the trees of the grove grew delicate roots into the outer layer of the defender's hide, provided additional nourishment, with the support of the dryads. However, after it was roused to fight, a defender was voracious, devouring slain foes and giving chase to those that fled.

An oaken defender grew according to its age, the size and health of its grove, and how many creatures it had consumed. Some could reach gargantuan size. However, a defender could grow small or even shrink if its grove was stressed, as it prioritized the dryad's and the trees' health above its own, and would even let itself starve to save them.

An oaken defender was a genderless creature with a unique method of asexual reproduction. Once it reached a thousand years of age, the defender received an acorn from the dryad's tree and incubated inside a follicle within its body. The defender absorbed additional nutrients from the grove and supplied these to the acorn, until it grew into an embryonic defender within an egg-like seed or cyst. It grew for another century, until it was approximately a quarter the size of the adult; the enlarged cyst caused its body to be noticeably distended. The dryads cared for the aged defender, gave it comfort, and said their goodbyes.

Finally, the young defender burst out of the body of the old, which necessarily died, having sacrificed itself. The dryads helped the young one acclimate and settle into its new life and duties, taking the place of the old one. The remains of the slain defender provided enough nutrients for the young one to soon have a growth spurt. Occasionally, there were not one but two acorns, and the second young oaken defender would depart and take up with a new grove.