Silverwood

Silverwood Trees, also known as World Trees, are semi-intelligent plants with a large variety of abilities. They are very rare, only produce seeds every few hundred years, and can't be transplanted due to their extremely complicated, delicate, and extensive root systems. Cal and Dungeon Eternium have Silverwood trees, and several other dungeon cores apparently do as well. All elven cities are also built around Silverwood trees.

Duplication
If given the pattern, they are able to duplicate any living creature, including dungeon cores. In nature, this normally manifests in their "seeds" which are actually just crystal orbs with a tiny copy of the tree inside. It is possible that dungeon cores were created as an attempt to mimic that ability.

Fertility
Silverwood pollen greatly increases fertility, which makes elves covet it as they are naturally very unfertile.

Ascension
Silverwood trees appear to be able to give a boost when in the tower, allowing you to reach levels you otherwise wouldn't have.

Essence Sink
They seem to be able to absorb nearly limitless amounts of essence and mana, as shown when Cal was funneling all the world's essence to himself and every drop of the excess was absorbed by the tree.

Ranking
All Silverwood trees are naturally S rank from first sprouting. How this works without vastly limiting the advancement in the tower of ascension is unknown, but it is likely that they are all simply treated as one being.