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"'You're probably thinking: who is this?'"??? is a new NPC added in v1.3 (Rushing Through). He is unlocked after getting the Good Ending (grab the medal, and return to the surface). He unlocks Boss Rush, to practice and master bosses.

After getting the Good Ending, he will simply appear in the Main Area.

Boss Rush
In Boss Rush, one player must face against all bosses in the game, in a row. Of all four area's, first two Minibosses must be fought, and then the main boss. The starting items are limited, but adjusted for better play.

The player starts with a Iron Sword, a full Health Potion, a Trading Scroll, and 3 Steaks.

All bosses give rewards. Minibosses give a few resources, and after each pair a chest of items is granted. Bosses give more resources and two random Boxes (White, Blue or Yellow). All bosses may also drop some food.

Gold can be used for treasure or the Trading Scroll; Tears can be used to refill the potion; Leather, Iron and Diamond can be used to create armor (a Pickaxe is given, but doesn't do anything else).
 * The reward for completing the game is 20 Rubies.
 * The last boss, Raimor, has less health and no fifth phase, to compensate for the lack of attack power.
 * This mode is separate from the Dungeon, and can be played when others are playing something else.
 * As normal, if you die, you lose and have to start over.

Story (heavy spoilers!!!)

 * This NPC is actually Gyranus, the God of Water. (This will become clear in Sapphire Caves.) In a desperate attempt to give him the Ruby Medal to stop the Void madness from happening, he abandoned his guarding spot and tried his luck by coming to Ruby Caverns. However, the dungeon went too deep, and even though he could replicate the fights almost perfectly, he could not manage to deliver the Medal and restore the balance much earlier.