The snowy snatcher would be a mob that appears in the mountain/snow biome and would appear as a 3 by 3 square of dark snow. When the player walks over the dark snow they will be thrown into the air and a large mouth would appear under them. While in the air the player has 2 options throw a item into the mouth or try to avoid the mouth. If a player throws an item into the mouth the snowy snatcher surfaces and you can try to run away or fight for your item back. If you land in the mouth you would be chewd up and spat out of its mouth doing heavy damage to armor and damaging the player. The player would be allowed to just walk around the snow but if your not paying attention you will pay a price.
This was just a quick idea I had so I dont have a lot planned out like attacks and drops but I hoped you enjoyed my idea.