Buy RS3 Wood spirit
The RS3 Wood spirit is a stackable item that helps with Woodcutting. When you chop a tree while holding a wood spirit of the same type, the spirit is used up and you get an extra set of logs. This doubles the logs you get from each chop. The extra logs do not give extra experience.
Wood spirits work well with other gear. With a Seer's headband, two spirits are used at once for four sets of logs per chop. With a sign of the porter, one spirit and one porter charge are used, and both logs go straight to your bank. They do not work at divine locations.
These spirits weigh nothing and are tradeable. You can store them in a wood box after finishing the Unwelcome Guests quest and building the Grove in Fort Forinthry. You can even use them right from the wood box.
Wood spirits also matter for high level players. You need 100 of each type, including oak, willow, yew, magic, and elder, to craft the hatchet of bloom and blight. That hatchet came with level 110 Woodcutting. Grab wood spirits to gather logs faster and save time.