You can do it! This room has a trick to it. Once you understand the trick, it's not so bad
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×In this room, Beethro's going to get stuck in a very small area while a mimic needs to move in a larger area killing roaches. The room is impossibly hard if you immediately kill all the roaches within reach of the mimic. You'll need to use those roaches to push the mimic around before killing them.
How to start the room (detailed instructions):
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×Get rid of the monsters that have the most room to run in.
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×Enter from the west with sword pointed east.
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×Step NE, so the western roach queen won't run away, then kill her.
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×Use the decoys (orange potions) to kill roach queens at (1), (2), and (3). The third decoy makes the NE corner easy.
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×Kill the seeps.
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×Use the first mimic to remove the roach queen and the seep from the NE coner.
How to do the SW corner (detailed instructions):
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×Here's where you have to use the trick. You have a roach queen and a seep to the south, and a bunch of roaches north of them. You'll have to use roaches spawned by the queen to push the mimic north to the other roaches. This works especially well if Beethro is directly north of the mimic.
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×Place the second mimic one square N of the queen.
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×Kill the seep. (It should be right next to the queen.)
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×As soon as roach eggs appear, kill the queen, turn sword SE (out of the way), and step N twice. Don't kill the eggs.
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×Look what happens when the egg matures. The roach moves directly S of the mimic. That's because Beethro is directly N of the mimic. Now you're set!
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×Turn sword N, and move Beethro N and S until the mimic is as far N as possible. Kill all the remaining roaches.