Planeswalker/Igniting

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

Planeswalker	Ignited on	Planeswalked to	Ignition's cause
Ajani	Naya	Jund	Realizing the death of his brother
Arlinn	Innistrad		Realizing she transformed into a werewolf and had killed an angel
Chandra	Kaladesh	Regatha	Striking against her executioner with pyromancy
Daretti	Fiora		Being crippled by the explosion of one of his constructs
Domri	Ravnica	Naya	Being buried alive as part of a Gruul ritual
Elspeth	A phyrexianized plane	Theros	Fleeing from the Phyrexians
Gideon	Theros	Bant	Realizing the death of his irregulars through his own hubris
Huatli	Ixalan	Kaladesh (uncompleted)	Under furious attack by Angrath
Jace	Vryn	Ravnica	Accidental planeswalk after being memory wiped
Jaya	Dominaria	Elsewhere on Dominaria	Hit by Jodah's mirror
Jeska	Dominaria		Being split from Karona with the Mirari
Karn (1st time)	Dominaria		Acquiring Urza's spark
Karn (2nd time)	New Phyrexia		Acquiring Venser's spark
Kiora	Zendikar		Being swallowed by a big sea serpent
Liliana	Dominaria	Innistrad	Turning to black mana to restrain her undead brother Josu
Narset	Tarkir	Pulled back to Tarkir	Learning the truth about Tarkir's past
Nicol Bolas	Dominaria	Meditation Plane	Rage against Ugin
Nissa	Zendikar	Lorwyn	Witnessing Emrakul's sealed presence
Nixilis	A plane of eternal war		Realizing the futility of life and mono-planar ambitions
Sarkhan Vol	Tarkir		Channeling the spirit of an ancient dragon
Samut	Amonkhet	Theros	Experiencing euphoria and joy after being thanked by Hazoret
Sorin	Innistrad		Becoming a vampire
Tacenda Verlasen	Innistrad		Defeating her sister Willia, and absorbing the Bog Entity.
Tezzeret	Esper	Grixis	Being attacked by guards after learning that the Codex Etherium was empty.
Teyo Verada	A plane plagued by diamondstorms	Ravnica	Being buried alive.
Tibalt	Innistrad		Feeling all the pain he had inflicted on others in his life
Ugin	Dominaria	Meditation Plane	Realizing his twin brother doesn't love him and is trying to manipulate him.
Urza	Dominaria	Unknown	Enduring the Sylex Blast and being resurrected through the Might- and Weakstone
Vivien Reid	Skalla	Unknown	Seeing her world destroyed by Nicol Bolas
Vraska	Ravnica	A dark tomb with no way out	Fleeing from guards that attempted to kill her
Vronos	Innistrad	Esper	Fleeing an attack by werewolves