In the latest of TF2's seemingly eternal supply of updates, the mercs are faced with their most outlandish threat yet.
The update brings four new community created maps, some of them 'Invaded' versions of existing maps and others entirely new. The Watergate map introduces a new 'player destruction' mode, in which both teams have to collect beer from dead players and deliver it to a UFO in the middle of the map.
It's set up in much the same way as the Gun Mettle Update, with an 'Invasion Community Update Pass' available from the store which gives you a coin that tracks kills on invaded maps for the month that the event lasts. You don't need to buy it to access the maps, and all the money raised goes to the update's community creators.
Buying the pass also makes you eligible for random drops of 'Space Cases' that can contain anyone of a bunch of the new cosmetics that have also been added. When Valve have done similar things with CS:GO, I've often been able to make back the money by selling my first couple of crate drops—so long as it's in the first day or two before the price of them comes crashing down on the community market.