Doggo is a decent monster for most decks, and incredibly useful in specialised ones, such as control decks. Its ability is to return a card back to the user's hand. Cards sent back to the hand will have all buffs/(but not KR)/other effects removed from them and their stats reverted to their original state fully healed. This won't work if you have a full hand, instead the card will be destroyed, this is useful if you want to initiate a Deathrattle. Doggo is especially useful for the Integrity