The Great Tree

The tree forms the center of Arbor and provides much to its citizenry, the tree stands just over a mile tall and its base is nearly a half mile around as well. The tree has a massive canopy that extends well beyond its trunk and most of the city is as a result covered in perpetual twilight. The tree, however, does bear fruit frequently and the citizenry relies on it for their main food source. They will also take chunks out of the tree to use for building materials and a few of the more expensive places to live are actually in the tree itself as a result.
The great secret of the tree is that it is alive and aware of the tiny creatures that have grown up around them, the tree is very old older than the city as the city was built around it when it was a much smaller version of the grand state it is in today.
The tree is also somewhat responsible for the effect of the objects in its domain, a plethora of objects are made or partly made with its wood and the trees unique nature lets it give rise to the creation of the living objects given enough time and exposure to other sentient creatures.
The tree has not sat idle though, It has found someone to find these objects before they become dangerous neglected things and develop a hatred for their former owners.