The purge just spawned under the map and started climbing through my foundations. Half my base and a lot of thralls have been lost 
Greetings @Craigarmstrong ,
Thank you for reporting this issue to us, but could you please use the given Bug Report Template?
This template has most of the information we need to start investigating and will make the process a lot quicker for everyone 
You can find it here: NEW Bug Report Template
If possible, please also add a screenshot.
Thanks in advance!