The Vord are an insect-like race that utilize several tactics to quickly overrun enemies and enemy defenses. There are several forms of Vord that appear during different phases of invasion. The Vord are nesting creatures and are responsible for the croach. Before the events of Codex Alera, the Vord had attacked and wiped out several tribes of the Marat.
In Furies of Calderon
The Vord are initially introduced as the "Wax Spiders," dog-sized creatures that maintain the croach and will attack anything that damages the croach. Tavi and Kitai are tasked with collecting the Blessing of Night, which only grows in a tree at the very center of the Wax Forest, which is entirely covered in croach. During the course of their collection, they're forced to take extreme measures to escape. Because of this, the queen of this group is awakened.
In Academ's Fury
Doroga informs Isana, Bernard and Amara that a large number of Marat were killed recently destroying a Vord nest. They had traced the movements of the Vord in three directions from the Wax Forest, which has now been completely abandoned and the remaining croach has died. The first was the nest they attacked. The second was in the direction of Aricholt. The final was in the direction of Alera Imperia along which they found Tavi's bag from his previous encounter with the Vord. Isana leaves to warn Tavi of the potential enemy and ask for reinforcments.
Bernard, Amara, and Doroga arrive at Aricholt only to find they got there too late. Most of the townspeople are already missing. During the investigation, several of Bernard's own men were captured by the Vord. Bernard sends for help, but goes ahead with an attack on the Vord nest, which is in a cave. The attack initially looks successful, with no remaining Vord in the cave. The group quickly discovers this was just a ruse and that the queen and her army are actually outside and have them pinned in. The Vord queen offers to let the group escape if they allow themselves to be Taken. The group refuses and plans to hold out as long as they can against overwhelming numbers.
Once in Alera Imperia, Isana is attacked by Kalare's men before she can tell Tavi or the First Lord about the situation. She is rescued by Fidelias and makes a deal with the Lady Aquitaine to send reinforcements to Calderon and to make sure Tavi is okay in exchange for her votes as a Citizen. Lady Aquitaine dispatches troops to Aricholt and decively turns the battle against the Vord.
Also in Aleria Imperia, we find that the Vord have formed a nest in The Deeps. They have been taking the Canim. Ambassador Varg has noticed discrepancies with his guards and makes several attempts to talk to the First Lord about it. Unfortunately, the First Lord has been (unknown to most people) incapacitated and there is currently a look-alike in his place. Varg eventually successfully gets the attention of Tavi and alerts him to the matter, making the Vord nest in the Deeps known. Tavi attempts to warn about the upcoming attack, but it's too late. Max and Tavi successfully defend the incapacitated First Lord while Lady Aquitaine destroys the assault from behind. All of the Vord except for the queen are wiped out.
Forms of the Vord
Before the main invasion force appears, the Vord will send out small rodent-size parasites. These parasites take over the host and, during the initial phase, will just lead the host back to the Vord nest. The Marat refer to the hosts as the "taken". Once they're taken, there's almost no hope of ever recovering the original person's consciousness. If the host could previously control furies, this ability is lost until furycrafting is used against the taken host. When fighting, the host will have little concern for its own life and will ignore most pain.
The Vord warriors vary depending on the target of the invasion. The parasitic version returns samples of their target and the warriors assume a similar, but different form. They don't use any weapons directly, but are incredibly strong, fast, have swordlike appendages, and are naturally extremely well armored. The warriors are known to have a weakness on their back - a croach-filled sac. It acts as a sort of breathing apparatus. Once destroyed, the warrior will soon smother to death.
The Vord queens also vary. They are extremely fast, strong, and tough. During an invasion, a queen will quickly create a nest and send out two other queens to form their own nests. Queens are known to have telepathic abilities and can, if within a certain range, control enemies that are not yet under control of the parasites.
Keepers, also known as the "Wax Spiders," are dog-sized spider-shaped creatures. They maintain, feed, and feed off of the croach. If any portion of the croach becomes damaged, the Wax Spiders quickly appear to investigate the site and will attempt to kill any potential foes. They are known to see in infrared, but can also switch to the visible spectrum.