Aloeswood
Agarwood, oud, lign aloes
Botanical name:
Aquilaria agallocha, Aquilaria malaccensis
Family:
Thymelaeaceae
Origin:
Asia
Part(s) used:
Wood
Special constituents:
2-(2-(4 methoxyphenyl)ethyl)chromone (27%), 2-(2-phenylethyl) chromone (15%), oxoagarospirol (5%) and many others (source: Ishihara et al., 1993)
Correspondance:
14 (Cunningham), 13,25 (Crowley)
Uses:
Incense, essential oil, aphrodisiac.
Aloëhout 
Aloetræ Just to clarify: Aloeswood has nothing to do with Aloe plants. Aloes are succulent plants of the genus Aloe, Aloeswood comes from a tree from the genus Aquilaria.
Aloeswood is one of the most expensive natural products existing today. Originally the Aquilaria-species were found from eastern India, through Burma, Bangladesh, Thailand. Indochina, to New Guinea and Borneo. Now, because of the trees being so highly estimated, and thus sought for, the natural range is much smaller. Read in this link about an interesting project concerning growing Aloeswood.
The tree itself is not enough; to get the product "Aloeswood" or "Oud", you need the presence of a certain group of fungi imperfecti. (Some sources claim, though, that you don't need the fungus at all, but only need to harm the tree mechanically). The attack of the fungi initiates a defence process in the tree, causing it to produce resin. This resin contains the valuable aroma. Trees who has been infected a long time ago are the most sought-after, and virtually non-existent today. It's more common to either grow the trees, or find a tree in the wild, wound it, and wait for the fungi.
A tree more recently infected can be harvested and used for oil-extraction. Older trees with a lot of resin are sold in pieces. The more infected, the better; even dead trees are useful. The largest pieces of such trees are sold for ten thousands of dollars. One particular piece is owned by the japanese royal family, and is frequently exhibited along with the other treasures.
The odor of Aloeswood is very special and cannot really be compared with anything else. You have to try it yourself! It is sweet, balsamic, at the same time earthly and divine. It is very sensual, and is therefore used as an aphrodisiac. It is uplifting, and gives energy, but in a calm sort of way. It is warming if you feel cold, and cooling when hot. It is archaic, holy, overwhelming.
It is still in use in Chinese traditional medicine, as an aphrodisiac, against an array of stomach disorders, and against cancer.