Guild Wars 2

i mystic forge 3 lvl80 hammer and 1 mystic forge stone… and get back a lvl80 exotic warhorn.

Is it because of the mystic forge stone?

I remember trying with 3 exotic dagger and 1 mystic forge stone and got back an exotic dagger.

I’m not sure what’s going on.

Apparently it is like a random item of the same rarity.

http://wiki.guildwars2.com/wiki/Mystic_Forge_Stone
“The stone takes the place of a fourth item of equal rarity, with a type and level equivalent to the average level of the first three items. For example:
Three Level 75 exotic axes + 1 stone = same as four Level 75 exotic weapons; result will be a Level 80 exotic weapon.”

Note that it says exotic weapon in the example given, not exotic axe.

Here is a thread with a short discussion about mystic forge stones.

Wrong subforum, btw.