Period Cube: Shackles of Amadeus

The player character's older brother has vanished, and the only lead is a clue that he was involved with an online RPG called Arcadia. They join the game to investigate — and are pulled inside by a mysterious light, waking up within its fantasy world. The rules are simple and stark: the only way out is to clear the game. The world itself is visibly coming apart at the seams.