New ghost mob in Minecraft

When you die, drop your stuff, and re-spawn, to get all your stuff back you would have to get past a ghost that spawns to guard your dropped stuff. It would be able to hover a block or two above the ground, and would be able to go through blocks. It would also not be affected by water, fire, or TNT. If you kill it, it drops a ghost helmet shard, and when you craft a helmet out of these, mobs don’t see you for ten seconds after you hit them(do they can’t find you while you hit them).