A list of Vendel's relationships with certain characters throughout the franchise.
Friends/Allies
Blinky Galadrigal
Blinky is Vendel's protégé. Blinky and Vendel seemed to get along well, but Vendel always felt skeptical of Blinky's conspiracy theories, believing him to be somewhat paranoid. He also thought that he puts too much faith in Jim, until he later grows to trust the boy just as much as Blinky has.
Eventually, he grew extremely fond of Blinky and thanked him for the news he gave him about the changeling in Trollmarket who helped Gunmar escape the Darklands, which could help clear Jim's name. In fact, Blinky was the last good guy Vendel spoke with before he meets with Usurna.
AAARRRGGHH!!!
Vendel has a close relationship with AAARRRGGHH!!!, despite him previously being a Gumm-Gumm before his reformation. When AAARRRGGHH!!! was nicked with Creeper's Sun poison and began to slowly turn to stone, Vendel tries everything to cure him, but sorrowfully admits that he knows nothing of a potential permanent cure. He also promises to keep this a secret from his friends as he respects AAARRRGGHH!!!'s well-being.
When Usurna arrives to Trollmarket and demands that she takes AAARRRGGHH!!! back to the caves, Vendel believes that it should be his choice if he wants to stay or go and even encourages the Trollhunters to win for AAARRRGGHH!!!.
Jim Lake Jr.
Vendel was initially doubtful as to whether Jim was fit to be the Trollhunter, due to his human status and inexperience with the troll world. Over time, however, he grew to respect and care for the boy in his own way, even expecting the impossible from him. Vendel did everything in his power to support Jim and protect him when his actions put him at odds with the Tribunal, mostly when Usurna tries to convict Jim for the release of Gunmar.
When Usurna revealed herself to Vendel as a servant of Gunmar and infects him with Creeper's Sun poison, Vendel's last words were a proclamation that the Trollhunter will stop her and her master, further indicating how much Vendel had placed his faith and trust into Jim.
When Jim discovered Vendel's death, he was completely devastated and blamed himself. Blinky, however, assured that Vendel gave his life believing Jim will save the trolls from Gunmar and Usurna.
Claire Nuñez
Vendel was at first against the idea of Claire entering Trollmarket, but his attitude immediately changed when she spoke to him in Troll language. He even wished that the Amulet of Daylight should've chosen someone like Claire who is very studious and hard-working (which offended Jim). Since then, the two have had a positive relation with each other.
Claire was saddened when she learns of his death.
Toby Domzalski
Like Jim, Vendel had trouble coping with a second human within Trollmarket. In "Return of the Trollhunter", he only allowed Toby in Trollmarket so that he could give Jim moral support.
In "Wingmen", Vendel trusted Toby to find AAARRRGGHH!!! after he disappears since he's well aware AAARRRGGHH!!! and Toby have a very close relationship.
Kanjigar the Courageous
It was implied that before his heroic sacrifice, Vendel and Kanjigar were very close friends. Vendel was deeply sadden to hear of his death by Bular.
King Fialkov and Queen Coranda
It is revealed in "The Big Sleep" that Vendel had met the king and queen of Akiridion-5 hundreds of years ago after the Zeron Brotherhood attempted to steal Gaylen's Core on Akiridion-5. He's shown to have a respectful posture towards the royals and proclaims that they have arrived just as an ancient prophecy foretold. The king and queen then gave Kanjigar Gaylen's Core so he can protect it from the wrong hands.
Barbara Lake
As he came to care about Jim, he was willing to help heal Barbara and remove the binding spell that links her to Strickler.
King Arthur
Vendel originally have a negative view of King Arthur from Arthur contently expansion his territory; However after seeing the threat of Gunmar and his army Vendel agreed to an alliance to help fight Gunmar and his army.
Enemies
Queen Usurna
Vendel and Usurna have initially been seen with a professional, yet strained, relationship. Usurna was often seen as a foil to Vendel's efforts and the two would get into heated debates. As members of the Tribunal, they were seen on opposing sides of whichever matter they needed to discuss. When Usurna revealed to Vendel in private that she was an agent of Gunmar, she immediately killed him to prevent him from clearing Jim's name (she did, however, state that she wanted Vendel to live long enough so he could watch Gunmar rule the world).
Luckily, unaware to Usurna, Vendel managed to record all of her evil doings so he can warn the Trollhunters that she is the real traitor who released Gunmar. This most likely implied that Vendel has always been suspicious of Usurna's real intentions ever since "Escape from the Darklands".
Gunmar
Vendel clearly sees Gunmar as an enemy.
Bular
Vendel clearly sees Bular as an enemy.