The air is getting colder around you

What was your reaction to seeing this message for the first time in Terraria and what were you doing? (This does not count if you saw it on the wiki beforehand)

I was underground for a long time checking out the underground hallowed snow and managed to rack up 1 platinum coin and about 10 new drops when suddenly that message popped up. I panicked for a moment as I was still fairly unprepared for any boss fights at all (I still had cobalt armor), so I teleported up to my base. Big mistake. Skeleton Prime popped out of nowhere and killed everyone. I tried fighting it but I was losing VERY quickly. So I ran as far away as I could, teleported back to spawn and ran in the other direction saying "They can't be doing this to me!" repeatedly. Luckily skeletron despawned and I was safe.