The crystal meter?

[Giga]

I have four meters in the upper right corner: hunger, cold, temperature, and a meter with a crystal icon in it that is slowly filling up.

What is this crystal meter? Am I supposed to lower it, and how?

This one: https://imgur.com/a/UNNRcyx

[Sanginius]

Thats the Countdown to base attack timer. Don't know what its officially called, but when the outer ring is full your base will be attacked that day. So thats the day you want to be at base at the start of the day.

[Mr. Fibble]

Time before an assault on the base.

You don't have to be there for it but being elsewhere reduces morale so it's better that you are.

If it's nearly full you can sleep to advance the timer just try and avoid having a lie in that day.

[Giga]

Cool, thanks. Turned out the attack on my base was two spitters. :P

[Sanginius]

They get harder :)

[snuggleform]

They never get that hard, provided you make walls they all funnel in and get rekt by followers.

One minor note I discovered recently is that the crystal meter doesn't fill at all until you get at least 1 follower.

[4kGamer]

mental note the base attack timer doesn't start until you get your first base survivor