Dann of Thursday is Van's armor, and one of the The Original Seven armors. Although originally part of The Original Seven, it was used by Van to fight every other member of the Seven.
In compact form it resembles a giant sword and thus wields a huge sword in humanoid form, from which a smaller knife can be separated. A giant blade is mounted on its back, and can provide limited flight capabilities similar to rocket propulsion. Dann is one of the few Armors which possesses no long range attacks, and it depends entirely on Van's movements and swordsmanship in order to inflict damage on its opponents.
Most unusual is its ability to instantly heal injuries or illnesses that Van has, including hangovers, once he enters the cockpit. Furthermore, it also has an Overdrive ability which can emit a highly devastating beam of supercharged G.E.R. fluid which cuts like a giant sword, although its hinted that this ability is Van's and not Dann's. Van, as a result of a special surgery, is symbiotically linked with Dann and is required to interface with the Armor at least once per week. If he does not, he will eventually fall ill as if with a bad fever and die. Accordingly, if either Van dies or Dann is destroyed, the other will cease to exist.
Dann of Thursday was originally a part of the first Original Seven. These 7 armors were built on Mother Earth, and used to police the planet The Endless Illusion. However, the first Original Seven became corrupt and were all nearly destroyed, with the exception of Gadved. Due to this, Dann and the other Original Seven armor's were stored in the Satellite ring above the Endless Illusion. Gadved, with the help of his Comrade, sought out new riders for each armor, with Gadved eventually finding Van. Van would meet Elena, who would help him hone his skills in controlling Dann.
In the beginning of the series, Van has not learned to activate all of Dann's power yet, but by the last episode he has discovered how to utilize Dann's electromagnetic shield, which greatly improves Dann's odds against a long range-attacking opponent. Later towards the end of the series Dann's satellite station was shot down by Saudade of Sunday. This stops Dann from repairing itself after its battle with Dahlia of Wednesday. Dann later repairs itself using Diablo of Monday's satellite station which is later destroyed by Saudade of Sunday. In the end, Dann is stored in another of the remaining satellites, though is not mentioned which one.