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	Date	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
Basri Ket	Amonkhet	Unknown		Elation at winning Oketra's Trial of Solidarity.
Calix	Theros	Unknown	~4562 AR	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	Between -2,500 and -440	Splashed by the blood of the corrupted angel Trine.
Freyalise	Dominaria	Unknown	~2434	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	4195 or 4196	Crushed by crumbling monoliths confronting Ravidel
Jaya Ballard	Dominaria	Elsewhere on Dominaria	2954	Hit by Jodah's mirror
Jeska	Dominaria	Unknown		Being split from Karona with the Mirari
Karn (1st time)	Dominaria	—	4205	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
Lukka	Ikoria	Unidentified plane		Overextending the power of the Ozolith
Narset	Tarkir	Pulled back to Tarkir		Learning the truth about Tarkir's past
Nicol Bolas	Dominaria	Meditation Plane	Between -20,000 and -17,000	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		Tortured by magical procedures designed to suppress his powers.
Ral Zarek	Ravnica	Unidentified plane		Being stabbed and finding out his lover was betraying him.
Ravidel	Dominaria	—		Being resurrected from the death by Kristina of the Woods.
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 (1st time)	Dominaria	Unknown		An experiment with time and phasing gone wrong.
Teferi (2nd time)	Dominaria	Unknown		Restored by 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	63	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