Even more content \o/

https://www.youtube.com/watch?v=aH6Lj7na8Ak

http://forums.terraria.org/index.php?threads/a-distinctly-etherian-update-terraria-and-dungeon-defenders-ii-crossover-coming-soon.50844/

Is it an update or a mod?

Fairly sure it's an update, as all the Terraria Twitterers were posting about it around the same time :D

I've never played Dungeon Defenders but this looks way cool. Thank you for the heads up.

Neither have I, but know some that have.
More challenge in Terraria is always entertaining \o/

Update should arrive sometime today, at some unspecified hour in some unspecified time zone (so, possibly tomorrow actually).

Done. :P

Time to contemplate starting a whole new world, yet again ;)

It's not necessary, all the new content is available from an old world.

But the waves will be different depending on which bosses have been defeated.

Not that the pre-hardmode waves should pose a challenge to anyone with hardmode gear.

I'm still a little vague on how this enters into the game. Is is pre Hardmode, Hardmode? Is it unlocked when I find something? Does the new NPC show up when a certain event happens? Does all the new stuff happen in sync with the classic "fight the Corruption/Crimson" plot line?

You need to find the new NPC. He can be anywhere. People have reported finding him on the surface near their spawn, others said he was in the underground. If you have a detector it'll appear as "unconscious man".

The tavernkeep sells a crystal and related stuff. You use the crystal to trigger the event. The crystal must be placed in a mostly flat, open area, so you can't cheese it too much by putting it behind a wall.

The event can be triggered at any point during the game progression. The enemies exist in several variants, so you'll get easy variants in early game and hard variants in late game.

It is not directly related to Corruption and Crimson. It's a different threat, an invasion from a different dimension.