Recently my guild accidentally did this on ossirian. Basically by doing this trick you spawn multiple crystals in one spot so you don't have to run around while doing the fight. All you have to do is get your hunter to send his pet to ossirian , and get the pet to attack ossi. When ossi has come down just a few steps have the hunter FD , and make sure noone has any aggro on ossi yet, (no buffs heals etc.) ossi should run back up the stairs. If you pay attention to the first free crystal you get , you'll notice another one spawns underneath it. Just do this trick as many times as possible to get as many crystals as possible and then pull ossirian.