Planeswalker/Igniting

Igniting (also "triggering", "flaring" or "ascension") refers to the spark's ignition, that is the process by which a sapient creature activates their latent spark and thus becomes a planeswalker.

Ascension
In Pre-Mending stories, planeswalkers were often sorcerers who somehow acquired the incredibly vast amount of mana required to perform the ritualistic sorcery of one's own ascension. Slaying a powerful planeswalker was one common way to acquire the necessary mana.

Sparking
Following the Mending, ascension was no longer a viable option for becoming a planeswalker, making it impossible for most wizards to become planeswalkers. A very small fraction of wizards possess the qualities needed for a natural spark. Usually, its ignition is triggered by a powerful, emotionally-affecting, perspective-altering life event, often a near death experience.

First planeswalk
As an effect of the ignition, the newly-ignited planeswalker planeswalks away for their first time: they are pulled to the Blind Eternities and then come back appearing to a random plane, and afterwards realizing their new traveling powers.

List of all explained ignitions: