Here are some Key to the Kingdom variants I've heard of, tweaked or come up with myself for those of us who love the game but want a little more depth or variety. I haven't come up with the details of certain of these house rules, such as player against player combat, but I encourage the players to do so. You're house, your rules. Please enjoy:
HEALTH POINTS – Lose all, go to Dungeon. Regain at space (Magic Stones,Wizard), or discard Food Equipment Card.
LIMITED EQUIPMENT – randomly assign set number of Equipment Cards. Some equipment to be collected. Allow players to steal Equipment Cards.
ADVENTURER CLASSES – Players gain proficiency with certain equipment based on a chosen class. Either increased success rate or automatic success with chosen equipment specialty. Players may start with certain Equipment Cards based on class, other Equipment Cards must be collected.
Faster Dungeon Escape - Rather than have to roll a 1 or 8 to escape and lose up to 3 turns if unsuccessful (Forever Dungeon), allow players to choose to give up an equipment card after any unsuccessful roll, then use that roll to move away.
STEALING WITH COMBAT - Rather than just stealing a treasure card when a player lands on another player’s space and then rolling to move away, players may fight for specific gear with a rock-paper-scissors (lizard-Spock) gear system and die rolls.
TREASURE ABILITIES - Reveal a Treasure Card to use its ability. May set use limit, roll for success rate, or require a 'recharge' at Whirlpool, Magic Stones, or Wizard.
Key: Get out of dungeons free.
Runesword: Defeat a Monster automatically.
Crown: Pass a Hazard automatically.
Cobra: Immunity to the Demon King (Cuz game recognize game), unless paired with the Key (Player must go to Dungeon but may also reveal the Key to escape).
Chalice: Allows the player to retry a failed obstacle or monster.
Ring: Allows players to steal by passing by another player rather than having to land exactly on their space.