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 creatures planeswalk 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 executor with pyromancy
Daretti	Fiora		Fleeing from the explosion of one of his constructs
Domri	Ravnica	Naya	Being buried alive
Elspeth	A phyrexianized plane	Theros	Fleeing from the Phyrexians
Gideon	Theros	Bant	Realizing the death of his irregulars through his own hubris
Jace	Vryn	Ravnica	Accidental planeswalk after being memory wiped
Jaya	Dominaria	Elsewhere on Dominaria	Hit by Jodah's mirror
Karn (1st time)	Dominaria		Acquiring Urza spark
Karn (2nd time)	New Phyrexia		Acquiring Venser spark
Kiora	Zendikar		Being swallowed by a big sea serpent
Liliana	Dominaria	Innistrad	Fleeing from her undead brother
Narset	Tarkir	Pull back to Tarkir	Learning the truth about Tarkir's past
Nissa	Zendikar	Lorwyn	Fleeing from the Eldrazi
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
Tezzeret	Esper	Grixis	Fleeing from guards that attempted to kill him
Tibalt	Innistrad		Feeling all the pain he had inflicted on others in his life
Vraska	Ravnica		Fleeing from guards that attempted to kill her