How can you get away with your sixth murder?
There has been an update, which made a few changes in the last Codex room :
- You have a dagger of gold in the start, and no other weapon appears through the entire level.
- The white skeleton mage has been removed in the last room.
- The Green slime has been replaced by a yellow scroll
Now, you only have one way to kill the last shopkeeper (sorry Aubergine) :
- Pick up the yellow scroll
- Prepare to throw the dagger
- Use the scroll, your golden dagger is now glowing.
- On the next beat (or move, for a bard), throw the dagger on the shopkeeper, this will kill him in one hit.
If you use the yellow scroll without preparing to throw the dagger, you will fail to kill the shopkeeper, as the gold weapon's buff will be canceled when preparing to throw.
Aubergine's answer works, but there is a more elegant solution using only the gold dagger. It relies on knowledge of the skeleton mage's wind spell and the gold weapon's ability to one-hit-kill anything if you attack after picking up gold.
When you enter the room, kill the slime. Do not kill the mage or pick up the pile of gold. Your goal is to use the gold to charge the dagger and kill the shopkeeper with that pile of gold. Unfortunately you can't just pick it up and throw- the throw takes two beats so it won't deal full damage.
To do this, you need to make the skeleton mage pull you into the gold on the same turn as you prepare to throw the dagger. The mage will do this if you are two tiles away when he would move. I.e. you need to be on opposite sides of the gold and the skeleton needs to be about to move (glowing staff).
Setting this up is difficult, especially since Bard can't skip turns. He can, however, waste time by trying to dig the walls here (don't worry about losing your combo. If you do things right, get into position and press the throw keys, you'll end up with this:
Next move, press up to throw the charged gold dagger and deal 999 damage to the shopkeeper.
Having cleared this last murder, the solution is much less complex than you would expect.
When you picked up the ring of war, you already managed to kill a shopkeeper with just a dagger (albeit the initial damage from the bomb helped). You now have two daggers. Just throw one at the shopkeeper to agro him and then finish him off with the second dagger.
Maybe there is a more elegant solution that relies on gold pickup and makes use of the gold dagger, but this did the trick for me.