Question: are all planeswalkers mythic rare?
Answer: Until War of the Spark, all planeswalkers had been printed with the mythic rare rarity, except for Ajani Goldmane, Jace Beleren, Liliana Vess, Chandra Nalaar, and Garruk Wildspeaker, which debuted in the Lorwyn block when the mythic rare rarity did not yet exist.