| ||My scars? No — they don't hurt.|| |
| - Xavier Lemmens, Thronebreaker: The Witcher Tales|
Gwalter aep Llwynog was a Nilfgaardian spy sent by Ardal aep Dahy who during the Second Northern War infiltrated in Queen Meve's ranks in order to kill her under the fake identity of Engineer Lieutenant Xavier Lemmens.
Gwalter joined Aedirnian forces few years before war started, where he was tasked with leading the defense from the East Tower of the city of Rosberg. When Nilfgaardian forces attacked the city of Rosberg, Xavier probably rigged the oil caldron, causing a fire in the tower which allowed Nilfgaardian soldiers to take the city and butchering its inhabitants, although Gwalter's face remained terribly disfigured in the action.
Gwalter acted to be senseless until Queen Meve of Lyria and Rivia, exiled from her own country by Count Caldwell, and her company, found him. Finally about to complete his secret task Gwalter, or better Xavier Lemmens, was taken into Meve's company.
In Angren, Meve ordered Xavier to build a makeshift bridge in order to allow her troops to pass over a quagmire.
At night however, when Meve was alone in her tent, Xavier attempted to strangle her with a rope, revealing his true identity. Fortunately for Meve, Reynard and Gascon arrived in time and saved her. Gwalter, died by Gascon's sword.
| ||I long awaited this moment... when we would be alone. You die now, Majesty. And with you dies Lyria's, Rivia's, the whole North's will to resist. Hael Ker'zaer! Hael—-|| |
|- Gwalter's last words, Thronebreaker: The Witcher Tales|
- In both concept art and Gwent artwork, Xavier's left side face is disfigured. However in the game dialogues it's his right side to be scorched.
- See the GWENT standalone game version card: Xavier Lemmens