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By Anonymous
How to kill Source Nightmare easily:
1. There is a large rock that is down-right to the Source Nightmare. Get all your characters to hide behind it.
2. Ungroup your fastest character. Send him/her to trigger the battle.
3. When it is the separated character's turn, make him/her run back to the rest of the group.
4. From there, the Source Nightmare can't attack you directly (It will try to but end up hitting the rock) and will summon 3 crabs to fight for him. However, they are fairly easy to defeat.
5. You can either summon stuff to fight the Source Nightmare for you or go out from behind the rock, use a long-range attack, and run back behind the rock.
6. Repeat until it's dead!