Hints:
Take out as much of the tar as you can each time before moving.
There is less tar than mud - and you will need to make sure that you end the mimic up in the right place.
Also, remember that the mimic is unkillable by the tar babies. So, kill the tar mother as soon as you can... but make sure that when you do, you will leave a shape of tar that can be cleared. This makes things a lot simpler. Don't worry so much about clearing the mud - it's a lot easier than clearing the tar.
If you're still stuck, I or some other helpful soul can provide a demo.
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