Jannar was an Arboreal scientist and one of his species' representatives on the Xindi Council. He was fair-minded, and a personal friend of Degra.
When Enterprise NX-01 was first sighted in the Delphic Expanse, Jannar spoke out against rash action, suggesting that the Council simply continue its pre-planned course of action and develop the Xindi weapon. Jannar may have had moral reservations about the construction of the weapon, but he swept them aside with a "better their world than ours" mentality. He said it was best not to think about how many innocents the weapon would kill, adding, "What we do is for... our children's future. Remember that." (ENT: "The Xindi", "Azati Prime")
However, Jannar voted against the development of the Xindi bio-weapon, decreeing that such a move was too dangerous. He believed that Degra must be given more time to create his weapon. He was very displeased when Commander Dolim had Rajiin infiltrate Enterprise to acquire information on Human physiology and anatomy; he said it put their entire work at risk. (ENT: "Rajiin")
Jannar was very skeptical of wild claims that Captain Jonathan Archer made about the Guardians and their role in building the Delphic Expanse spheres. He came aboard Enterprise with Degra to see Archer's evidence, but constantly pointed out that Archer could be fabricating it. Despite this, he actually could not explain what he was shown; he at least allowed Archer to present his case to the Council. (ENT: "Azati Prime", "The Forgotten", "The Council")
Once Archer did so, Jannar, like Degra, was fully allied with Archer. Arboreal vessels participated on the side of Enterprise in the battle to stop the weapon from being launched. After the weapon was en route to Earth, Jannar assisted Archer by helping to crew Degra's ship in Archer's effort to catch up to the weapon in time. (ENT: "The Council", "Countdown", "Zero Hour")
