I know krissy_punk has created a similar thread, but here's mine. First of all I am very sorry you have gotten griefed. Okay so before you tpa ANYONE to your island, make sure valuable blocks and items are locked and take screenshots of your island, this way if logblock fails you might have a chance of getting a refund. Now if you have proof of someone griefing, make sure to screenshot it. This may be a small guide, but it helps. Thanks for reading!
