Treant [Dark Sun]

This magical being fuses a tree of life with one of the water-dwelling spirits of the land. It looks exactly like the kind of tree it was made from, with bark skin, branch arms and a face formed by knots in the trunk, so a motionless one has a 95% chance of hiding within a grove. Practically immortal, it serves as the living guardian of a particular stretch of wilderness, often a grove of living trees of that kind, the way a common treant looks after an ordinary forest.

Being a made thing rather than a natural race, it has fixed abilities. Its bark grants excellent Armor Class against everything except fire, which strikes it at +4 with 1 bonus damage, and it has no magic resistance to fire spells, since fire opposes water. Each branch-like claw strikes for 6d6, it can lift creatures weighing up to 500 pounds, and it can hurl one boulder per round for 4d6. Unlike other treants it cannot animate trees.

Instead it has innate water magic. Once a day each, with no verbal, somatic or material components and an initiative rating of 2, it can use conjure elemental (water), create food and water, create water, lower water, part water, purify food and drink, reflecting pool and transmute water to dust.

Druids create these treants solely to defend the wilderness, and only when such a spirit volunteers, so they are extremely rare. A spirit is actually stronger in its natural state, with more magic and physical might, but it is inattentive and often waits until enormous harm is done before acting. Bound into a treant it is tied far more tightly to the physical world and responds much faster to life-draining wizards and other despoilers. While bound it remembers nothing beyond its treant existence, and it cannot leave until that body dies.

Each one guards a specific site and defends it without fear, because death means nothing to it. It will die for the wilderness, yet otherwise looks after its own survival and will never sacrifice itself just to release the spirit.

The druid builds a special tree of life to house the spirit, persuades the spirit that the change is needed, then casts three spells: tree of life, reincarnate and liveoak. Persuasion is hard, because once the spirit leaves its pool or stream, the water swiftly dries up.

Barring violence the treant lives forever. If it is slain, the spirit escapes unharmed but cannot form a new body for as many years as it spent in the tree. Afterward it remembers both its time as a treant and its earlier existence, and its old water source slowly returns unless its bed was completely destroyed.