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If you are tier 0: You can attack or be attacked by anyone
within 10 levels.
If you are tier 1 or higher: You can attack anyone in your
tier and higher. You can be attacked by anyone in your tier and
The easiest way to check your range is to check the who list. If
their tier number is red, that means you can attack them. If the
brackets are red, that means they can attack you.