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		Becoming a werewolf
Chandra	Kaladesh	Regatha	Fleeing of her executioner
Daretti	Fiora		Fleeing of the explosion of one of his constructs
Domri	Ravnica	Naya	Being buried alive
Elspeth	A phyrexianized plane	Theros	Fleeing of the phyrexians
Gideon	Theros	Bant	Realizing the death of his irregulars
Jace	Vryn	Ravnica	Accidental planeswalk after being memory wiped
Karn (1st time)	Dominaria		Adquiring Urza spark
Karn (2nd time)	New Phyrexia		Adquiring Venser spark
Kiora	Zendikar		Being swallowed by a big sea serpent
Liliana	Dominaria	Innistrad	Fleeing of her crazed brother
Narset	Tarkir	Pull back to Tarkir	Learning the truth about Tarkir's past
Nissa	Zendikar	Lorwyn	Fleeing of the Eldrazi's presence
Nixilis	A plane of eternal war		Realizing the futility of life and all his killing ambitions
Sorin	Innistrad		Becoming a vampire
Tezzeret	Esper	Grixis	Fleeing of some guards that attempted to kill him
Vraska	Ravnica		Fleeing of some guards that attempted to kill him