Heaven Monsters are new monsters created by LHK. They are colored very dark blue, while they are stored in Main Deck, and not in the Extra Deck.
How to Heaven Summon[]
To Heaven Summon, you need a monster and an item that should be either in your pocket or in the table (a pen, a USB stick or a toy car are acceptable, a truck is not). Send that monster you control to the Graveyard and send the item to a new Zone called Item Zone, which is next to the Graveyard. You have performed a Heaven Summon.
Like Xyz Monsters that have "detach", the Compositions that have "deactivate" and the Ultima Cards that have "dismiss", the Heaven Monsters have "throw", which allows you to throw any item from the Item Zone to the left of the playing mat as part of the effect.
Items can be placed or thrown by not only other Heaven Monsters, but also by other card effects, such as other monster effects or Spell/Trap Cards.