An immolation cloak grants its wearer resist fire 20. As a swift action, the wearer can command the cloak to burst into flame, providing the benefits of a fire shield (warm flames only).
The wearer can dismiss the flames as a free action. The cloak can be used for a maximum of 10 rounds per day, which don't have to be consecutive.
By expending one use of mythic power, the cloak's wearer can recharge its immolation abilities. In addition, the wearer can expend one use of mythic power to detonate in a fiery explosion, dealing 1d8 points of fire damage per character level in a 30-foot-radius spread. A successful Reflex save (DC 10 + the wearer's mythic tier + the wearer's Charisma modifier) halves this damage. Though apparently destroyed in the explosion, the wearer reforms just prior to the start of his next turn in the space he exploded in (or the nearest open space if that space is unavailable).
Last bolded part is the bit I'm interested in. Does this mean you can (for 1 mythic power use) disappear from the game, becoming untargetable for a round and potentially deal some pretty good damage too?
Yes it is a Mythic item, and yes it does cost 65,000 to buy, (though you'd most likely be crafting the item as a DM who gives out Mythic Magic Items should seriously reconsider the idea) but it seems a little too good as you can use it for some really good escape tactics as it can't be countered by Dimensional Anchor effects.