This is a special transnformation for arrancars. You see, when a mommy and a daddy really love eachother, oh crap, wrong speech. Listen, the metamorphisis can only be obtained by the first 5 arrancar if they are an admin/have 350 posts. And you need to have good rp skills. Here's the info:

The metamorphisis is a change that arrancars that are ranked 1-5 have. This is permanent. It increases your power by a lot, and changes your appearence, attacks, zanpaktou, and your mask. You need to post a new character profile that tells us it's a metamorphisis in the title. The you make a new ressurecion. You must also ask for permission from me. Other than that, you must follow all rules.