From the tomes of Alzahakar the Sage:

Legend tells of fierce creatures made of pure magic that attack nodes. These creatures are called "Xeochicatl" after similar to the magic-eating monsters described on Ko'catan lore.

These creatures are drawn to the mana nexus found in this land, more commonly known as "nodes" by the layperson. They use the mana to feed themselves and grow stronger. It is said they can also consume mana from an adventurer to feed themselves as well.

A spellcaster's mystic connection to the nodes leaves him or her with a limited ability to sense when the creatures are attacking a node. This allows the spellcasters to organize a counter-attack to fight off the creatures. Be warned! They are very difficult to kill and less experienced adventurers should be cautious.

The four types of Xeochicatl are based roughly on the four elements of Faren's wild magic. An adventurer must be wary of each one and be aware of what magics they assail opponents with. Being properly protected can mean the difference between life and death. Do not think that just because they use magic that they are physically weak. They can tear a warrior apart in a matter of minutes with their bludgeoning fists and fast attacks.

The attacks on the nodes have dire consequences. Should the Xeochicatl remain on this plane long enough, they can take the energy from the node. This leaves everyone unable to pull from the mana provided by the node. There is a slight chance that the draining of the node can sever the mystic connection between the node and yourself, requring you to meld with the node again. During the time that the node is dead, no person is able to meld with it.

The Xeochicatl themselves are interesting creatures. Their magic is actually concentrated in the colored gems one sees in their body. Upon death, the energy from these gems meld into a single, dense stone called a heartstone. The heartstone is the essence of the Xeochicatl and can be used for various things. Currently, the fey that decorate the inn rooms are said to require the stones to create items to place in the rooms. Something as special as a storage chest, for example, requires one of each type of stone. I have heard talk that the priestesses are working on divising spells that use the magics contained within the stones, but these rumors are unfounded.