Spoiler Level 12
I normally don't comment here but as I was unable to find any walkthrough for diamond on level 12, it's just jumping towards it after you turn off the fires switch. It's a tiny maze but easy to figure it out once you're inside the block. Cheers!
 "The Wizard of elemental magic"){kind=icon}
 "Christmas cat"){kind=icon}
 "Doodle Devil"){kind=icon}