This achievement is not completable on a troll. What a weird bug to report, but apparently I’m absolutely too tall on the only 2 characters (trolls) that I am currently doing delves on because one of the chests is up on some platforms. This requires you to jump from one to the other, but instead of getting onto the next platform I’m stuck because I’m basically too tall to wedge into the space that has the chest . My husband was with me on his blood elf, not an issue for him. I was jumping just as he was, and to boot he sat down at my computer and tried to make the jump for me - it does not work. I even tried using a toy to make myself a blood elf - for some bizarre reason you seem to retain your normal size hit box despite your shapeshift? I guess that’s the best way I would describe it. I may do other characters in the future, however, this report is for the people who only have 1 character who will never make it to that chest. Please do not be racist against trolls, we can’t help it we are tall.
Most shapeshift toys do in fact modify your hitbox size, the one you used may be an outlier or it was a bug. Also try Noggenfoggers tiny effect.
All else fails, take a Priest in and have them life grip you in to the room.
At the end of the day they should still fix it. Like I said, I’ll eventually make it into delves with other characters. Although given their current track record for fixing things I won’t hold my breath.