Marc

"'Thank you SO much for rescuing me... how can I ever repay you?'"Marc is (or, at least, should be) the first NPC of Ruby Caverns to be encountered and freed. He unlocks the Ruby Pickaxe for all players, and appears in the Main Area to give "valuable" hints for 1 ruby.

In Dungeon

After you found a block of TNT and placed it in the wall, he will start talking to you. After the conversation he grants you the Ruby Pickaxe, which can mine Rubies, and unlocks it for all runs. Finishing the conversation makes him appear in the Main Area.

In Main Area

When talked to, he will say that he has read things about the Dungeon and would like to share his knowledge for a Ruby. Talking to him again grants the two options to click in the chat: [Yes, please] [I'm good] [Yes, please] will remove 1 ruby from your total count, and give you a random message with information about the dungeon. The information can be useless, already seen, or already discovered by the player. All options are immediately unlocked from the beginning.

[I'm good] will do nothing.