The Super Treasure is an infinitely long string of zeroes followed by the words “Super Treasure”. Since the Super Treasure is undefined (there is no clause saying that the Kings choose what it is, only that they must hide it), I believe it defaults to this.

(“If a game variable has no defined starting value, then that starting value is [...] the alphabetically earliest legal text string it may take (for a text string which may not be blank, with the digits 0 through 9 considered to precede “A”)”)

For good measure I’ll add that the Super Treasure is also a blank string, and also the string “Super Treasure”.