Skyhawks characters

Kain

Kain is a merciless kludd-like night creature, Apello and Asteria's brother, Ace's half brother, Kira, Feather, and Kaida's half uncle, Annie and Ciaran's uncle, and Firebolt and Levia's son. He appears as a black anthropomorphic wolf with giant bat wings and red eyes. He fights using a normal iron sword which lights on fire at Kain's will.

Kain is a ruthless warrior who shows little to no compassion or mercy towards enemies. He loves teasing his enemies and holds a ferocious grudge against Ace for defeating and nearly killing him on their first meeting. Kain was born to Master Levia and Firebolt. He claims to have been born in his animal-like form, implying to have been a genetic mishap. He declares himself to be immortal due to old age but young look. He was summoned by his mother Levia to be her champion. Later in season 3, Kain manages to overpower Ace and prepares to throw him to his death. He tauntingly reveals he caused the flood that killed Ace's brother, Kai under his mother's orders and attempts to assassinate the Skyhawks in a similar manner. Ace's son, Feather and his pet track beast Scout saves the former and gets his wing ripped. Ace throws Kain into the flood, saying his infamous line "This time, no mercy". He survives but is murdered by Zephyr's pet dire wolf Spirit while attempting to kill him and his sister.

Kain had a brief interaction with Shadow Stalk while trying to escape Terra Hallows which resulted in him breaking his wing and being permanently unable to fly. 

Kain enjoyed his rivalry with Ace and often referred to him as "Brother", nodding to the both of them being half brothers, having the same father, Firebolt. 

He is seen dueling with Kaida a lot. Kain seems to have a small amount of sympathy for Kaida, shown when hesitating to kill her when Levia instructs him to.

Aasira and Kain are also seen being rivals followed by Aasira's father Aerrow, mother Piper, brothers Pramesh and Zephyr, sister Celeste, and Apello and Ciaran.

Thea only talks to Kain when she insults him once.

Kain has had terrifying encounters with the Skyhawks mythical creature companions.

Kain and Nite hate each other.

Levia was the only person Kain truly cared about.

Kain never met Asteria but since she was Firebolt and Levia's daughter, she is Kain's sister.

Kain never meets Black Spade but is fully aware of and seems to be infatuated with her.

Trivia: 

Kain is the seventh character to die in the show. The firsts being Ida, Kai, Firebolt, Tinder, Shadow Stalk, and Webster. Others being Levia, Wand, Jay, and Celeste.

Next to his mother, Kain had the most brutal death in the series.

He is the possibly half night crawler.

It's implied Kain and Black Spade have romantic feelings for each other.

Kain can fly but his wing was damaged when Scout attacked him.

Instead of a whispery raspy voice like most night crawlers, Kain as a deep gruff voice.

He wears all black clothing with a red talon symbol on the chest.

He is also the third onscreen death. The first being Tinder. Second being Webster.