A sticker sheet! Just like when we were kids! But this one is a little more hardcore than those. Included on the sheet are:
Owl Bear
Gelatinious Cube
Beholder
Devourer
Mind Flayer
Myconids
Overall sheet measures 6.5" by 5.5". Making the stickers aobut 2" to 2.5". 
Made from thick, durable vinyl that is waterproof, UV protected, can last outdoors up to 5 years with a permanent adhesive. I have had a one of these on my car for about 4 years and can attest to its durability. They can also go through the dishwasher repeatedy.