The Lan Kin was a vine-like creature which feasted on grief. It was unable to take people against their will, and so enticed victims to grab hold of it by morphing into their deceased loved ones.
Aiming to feast on Tanya's grief, the great trunk of the Lan Kin tried to lure her in using the image of her father. Other branches took the forms of Rachel and Orla'ath, with the aims of feasting upon Ram and Miss Quill respectively.
Miss Quill compared it to a chameleon, because of the way it camouflaged itself and snatched its prey. (TV: Nightvisiting)