Valve have learnt their lesson from Diretide: don't deny the Dota 2 community their holiday celebrations. That means that Frostivus is back. The holiday event is traditionally quite lovely. Last year's Frostivus started normally before being taken over by The Greeviling, an update and game mode in which players can use their Greevil a secondary hero. At this point, I'd normally make a crack about how I don't understand any of this and don't care, but truthfully, I do understand it. It's just easier to be flippant than explain all the context. Instead, this time, I'll take door number three and link to the Dota 2 wiki page about the Greeviling event.
Who knows whether Greevils will return to cancel Christmas this time out. There's a plushie of one with a nail through its head on the Frostivus site so my bet is on whatever.
There's that old-fashioned flippancy. Anyway, from the Frostivus 2013 site, it seems the season of givening is returning, encouraging players to give in-game items as gifts to one another. Also, something about Wreath-Night: "Collect bright winter berries and sprigs of fir, and twist them together into mementos for family and friends. Doze off to the smell of simmering rumbutter, assured that the spirits of Frostivus Eve are conspiring to grant your wildest dreams of peace and friendship!" I genuinely don't know what that means but I bet it involves the new socketing system added in the last update. And isn't the word "rumbutter" just the most lovely smelling word?