Giant ent

Giant ents are level 78 Summoning familiars. They are foragers that produces oak logs, and have the ability to convert pure essence into runes. Giant ents are also useful in the Farming skill.

Giant ent pouch
Giant ent pouch is made by using a Summoning pouch on a Summoning obelisk with 124 spirit shards, a Green charm and a willow branch in the inventory. Making the pouch earns 136.8 experience points. Using the pouch to summon a Giant ent gains 1.6 experience points, and costs 8 Summoning points.

Acorn missile scroll
Acorn missile scroll enables the use of the Acorn Missile special move for a Giant ent. Using the pouch on a Summoning obelisk creates 10 scrolls.

Acorn Missile
Acorn Missile is a special move for Giant ents, which may inflict up to 170 life points to 3 opponents, as well as drop acorns.

Currently, it hits an opponent (or anyone around the opponent) twice.

Nature link
If a pure essence is used on the Giant ent, it will turn into either an earth rune or a nature rune. However, experience is NOT gained from doing this. It is also required to use each pure essence individually on the Giant ent which can be a very tedious effort.

A good method is to mine pure essence and give it directly to the Giant ent to convert. This can yield upwards of 400 earth runes and 500 nature runes an hour if the player is proficient at clicking.

Farming
Giant ents have the ability to potentially increase yield when harvesting fruit from fruit trees, bushes, cacti and nightshade, by 50%. This means that each time you pick a cactus spine, nightshade or fruit, you have a 50% chance of receiving two of the same. However, you will not receive experience for the bonus yield.

Trivia

 * Ents are a fictional tree-like race invented by J.R.R. Tolkien for his fantasy writings (e.g. The Lord of the Rings). They are noted for doing things, like speaking and their language in general, very slow and long-winded, epitomised by Treebeard's saying "Do not be hasty." The dialogue of the giant ent may be a parody of this.
 * Ents were once a random event in woodcutting that, if ignored and not walked away from, could break your axe.
 * As many others, its examine is a pun.
 * Even though Ents have a tertiary item of a willow branch, they produce oak logs.