Avar Kriss is a human female Jedi Master and the closest thing the High Republic publishing initiative has to a protagonist. She was introduced in Charles Soule's The High Republic: Light of the Jedi (Del Rey, 2021), the novel that opened the whole programme. Her homeworld has not been established in the published material.
The song
Her signature is a way of perceiving: she experiences the Force as music, and she can hear the individual lines other Jedi contribute to it. In the Great Hyperspace Disaster that opens Light of the Jedi, that lets her coordinate dozens of Jedi across a catastrophe as a single instrument — one of the most genuinely new pieces of Force lore anyone has added in decades, and a far better dramatisation of "the Jedi at their height" than any duel.
Marshal of Starlight Beacon
She is given command of the Republic's flagship frontier station, and the burden of the era's central failure lands on her: an enemy she cannot predict, a station she cannot save, and a public role in which being visibly the best of the Order becomes its own trap. Later phases — The Eye of Darkness onward — take her somewhere considerably darker than the opening novel would suggest.
Canon only
The High Republic era is a post-2014 construction. There is no Legends equivalent to Avar Kriss or to the era she belongs to — the older continuity's version of this period is unrelated and thinly sketched.
Reading note
Start with Light of the Jedi. It is the entry point for the whole initiative, and Kriss is the thread that runs furthest through it.