Cursed Blade is one of the three skins released under the Eye of the Void part of the Gladiators offer. It was available for purchase in mid July 2017.
Cursed Blade could be purchased for $4.99 in a deal that included 3250 coins. It could also be purchased for $19.99 in a deal that included the Orc Warrior skin and either 50000 coins (Browser) or 1800 DNA (Mobile). It was not available for individual purchase and may not be available for purchase in the future.
Details of this offer may vary depending on location and platform.