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. 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 Goldmane	Naya	Jund	Realizing the death of his brother
Arlinn Kord	Innistrad	Unknown	Realizing she transformed into a werewolf and had killed an angel
Calix	Theros	Unknown	Frustration about his inability to fulfill his purpose of following Elspeth Tirel.
Chandra Nalaar	Kaladesh	Regatha	Striking against her executioner with pyromancy
Dack Fayden	Fiora	Unknown	Witnessing his friend being killed by rival mages
Dakkon Blackblade	Dominaria	—	The planeswalker Geyadrone Dihada ignited his spark.
Daretti	Fiora	Unknown	Being crippled by the explosion of one of his constructs
Domri Rade	Ravnica	Naya	Being buried alive as part of a Gruul ritual
Elspeth Tirel	A phyrexianized plane	Theros	Fleeing from the Phyrexians
Eskil	Dominaria	Unknown	Splashed by the blood of the corrupted angel Trine.
Freyalise	Dominaria	Unknown	Mortally wounded by Jason Carthalion.
Gideon Jura	Theros	Bant	Realizing the death of his irregulars through his own hubris
Huatli	Ixalan	Kaladesh (uncompleted)	Under furious attack by Angrath
Jace Beleren	Vryn	Ravnica	Accidental planeswalk after being memory wiped
Jared Carthalion	Dominaria	Unknown	Crushed by crumbling monoliths confronting Ravidel
Jaya Ballard	Dominaria	Elsewhere on Dominaria	Hit by Jodah's mirror
Jeska	Dominaria	Unknown	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	Unknown	Being swallowed by a big sea serpent
Liliana Vess	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 and envy against Ugin
Nissa Revane	Zendikar	Lorwyn	Witnessing Emrakul's sealed presence
Ob Nixilis (1st time)	A plane of eternal war	Unknown	Realizing the futility of life and mono-planar ambitions
Ob Nixilis (2nd time)	Zendikar	Unknown	Siphoning the power of the hedrons into himself.
Oko	Unknown	Unknown	Subjected to magical procedures designed to suppress his powers.
Ral Zarek	Ravnica	Unidentified plane	Being stabbed and finding out his lover was betraying him.
Rowan and Will Kenrith	Eldraine	Unknown	Learning the truth about their birth mother.
Sarkhan Vol	Tarkir	Unknown	Channeling the spirit of an ancient dragon
Samut	Amonkhet	Theros	Experiencing euphoria and joy after being thanked by Hazoret
Sifa Grent	Grixis	Unknown	Tortured by Malfegor.
Sorin Markov	Innistrad	Unknown	Becoming a vampire
Tacenda Verlasen	Innistrad	Unknown	Defeating her sister Willia, and absorbing the Bog Entity.
Teferi (2nd time)	Dominaria	Unknown	Restoring of a Powerstone made by Jhoira.
Tezzeret	Esper	Grixis	Being attacked by guards after learning that the Codex Etherium was empty.
Teyo Verada	Gobakhan	Ravnica	Being buried alive.
Tibalt	Innistrad	Unknown	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 swamp on a dark plane. A tomb with no way out.	Being severely beaten by Azorius prison guards.
Vronos	Innistrad	Esper	Having his face scarred by werewolves