Sheens in need of recharging or repair plug into the power tree’s modules to recharge while the tree’s ten spidery manipulator arms do rapid repairs where needed. These repair routines “heal” damaged sheens at a rate of 1d8 hp per turn. Power trees can recharge and perform repairs on ten different sheens at a time.
Power trees never travel far from their cysts. A single power tree can fully recharge a sheen in 1 turn per HD of the sheen being charged and can charge up to 50 HD of sheens per day. Depleted power trees recharge in 4d6 hours in direct sunlight.
Power trees are heavily armored and have redundant systems to ensure their continuance. For this reason, these sheens can repair damage inflicted to themselves at triple the normal rate of other sheens.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.