im sort of new here and dont who wot it is could ne 1 tell me how to use it?and can use it on bosses?

If you cast vanish on an opponent and it disappears, then one use of Doom wil kill it. X-Zone is the same as Doom, but i dont think you get any items from the enemy. And yes, it does work on most bosses. Makes the game way too easy though.

My advice, NEVER use X-Zone in this way. You WILL miss out on a lot of things. If you're fighing an undead enemy (Doom Train, Doom Dragon, etc.), you can use Life, Revivify, or Phoenix Down to kill them the same way as you can use Doom to kill a living enemy. The only enemies that this won't work for are the ones that you can't cast Vanish on.