This game is brilliant, but I thought I should probably write this walkthrough because others seem to be having some difficulty.
WALKTHROUGH - DON'T READ IF YOU WANT TO FIGURE THINGS OUT YOURSELF:
When you're the Murderer, any time the King does something, he's about to turn around, so stop charging.
When you're the King:
- Mace-wielding enemy: Most risky. You have to turn around when the mace is behind his head for the least risk. He becomes the King if he kills you, but the game doesn't end.
- Jester: Second-most risky. Turn around when he starts charging his attack. If you're killed by him, he'll throw your crown away - ending the game and granting you the 'Whyyyyy?' achievement.
- Weaponless enemy: Can be stopped at any point. If you allow him to hug you, the game will end and you'll be granted the 'Love Always Remains' achievement.
- Green drink enemy: Can be stopped at any point. If you allow him to tap your shoulder, you'll be poisoned and will die. He becomes the King if he kills you, but the game doesn't end.
- Red drink enemy: Can be stopped at any point. If you allow him to tap your shoulder, you will no longer die of old age (but can still die by being murdered). Once you reach the end of the hallway, the game will end and you'll be granted the 'Eternity' achievement.
'Party in the Dungeon' achievement: Any time a Murderer (including you) is caught, they'll be thrown into the dungeon and become a skeleton. Once enough Murderers are caught, one of them will get a party hat and you'll be granted the achievement. Warning - if the game ends the dungeon will reset.