He is lanky. He has a round face.
Jonneth was found in the Two Rivers by Mazrim Taim and brought to the Black Tower. He is one of the most skilled of the Two Rivers Soldiers. He, along with Emarin, Canler, and Arlen Nalaam are leveling hillside with the One Power. Alongside them is a group of Taim's men led by Coteren.
Coteren mocks Androl Genhald who has stopped by and embarrasses him in front of everyone by showing how weak he is in the One Power. Jonneth's group become furious and everyone fills with saidin, just about leading to open battle between the two groups before Androl manages to calm them all down by making light of the situation. After Taim's group leaves, Androl agrees that they will start to investigate the bizarre changes that are happening to people.
Some time after he still has not been raised by Taim, despite being as strong and skilled as any Dedicated. When Welyn returns to claim Logain and Taim have patched up their differences, he is openly doubtful and questions Welyn on it. He only stops when Lind Taglien distracts him. Jonneth is part of Androl's group to sneak into the the Black Towers foundations, where Taim has had hidden rooms constructed. During the attempt to rescue Logain, he was able to kill Coteren with a bow and arrow. They then find Logain in a cell. Before they can escape, they are found by Taim and his men after Evin Vinchova reveals their plan. They are pinned in the cell until Taim brings the roof down on them knocking the group unconscious. Jonneth is held captive, while Evin is taken away and Turned to the Shadow.
After the Black Tower was freed from the Shadow, Logain promises to raise Jonneth to full Asha'man; he stays at the Black Tower with his friends even though he could be claimed by an Aes Sedai. Androl then meets with Canler, Emarin and Jonneth. They are concerned about Logain changing after being subjected to the Turning process several times. However, they are loyal to what he decrees. Androl is concerned that Rand knew about the trap at the Black Tower and didn't help them. The men decide that they will take Rand's last command to heart and fight to live, rather than to die. They are not minions of the Dragon Reborn or the White Tower but their allegiance lies to the Black Tower only.
Before the Last Battle starts it can be supposed that Jonneth is raised as a full Asha'man.
During the Last Battle he fights along Androl, Pevara and Emarin, while Theodrin starts following him around and Heals him after they escape Demandred. She seems very fond of him and Pevara tells to Androl that Theodrin wants to bond Jonneth as Warder.
Along them he disguises himself as a non-descript Darkfriend when they go to find and steal back the Seals.