“In Theory” that particular Mytic will be in the Event Chest during the next Blight Lands Event and you would need about 1,000 Event Keys to have an approximate 2/3 chance.
“In Practice” You will need to have AT LEAST 3,000 Event Keys and an absolute Mountain of Gems saved up if you want a copy (possibly some extra real money to buy more Gems too).
Good Luck, you’ll need it.
I would personally wait for Crafting to arrive in 3.1.