Zelda series producer Eiji Anouma explained on Miiverse why the Twilight Princess returns in Hyrule Warriors as Twili Midna rather than her more familiar form.
"When I was developing Twilight Princess," Anouma wrote, "I thought it was such a waste to let a beautiful princess like her only appear in the ending. Now Koei Tecmo Games has made my wish to see more of her come true."
Twili Midna is partnered with her weapon of choice, the Mirror of Twilight as also seen in the 2006 Zelda game. The DLC also includes a smattering of extras including an adventure map and some costumes, one of which lets you dress Link as a familiar Zelda character. According to Anouma, that costume "may make you say 'Wow!'" Here's hoping it's the Old Man from the first Zelda, complete with a big, fake joke-shop beard.
The Twilight Princess Pack is $8 on its own or you can get it as part of the Hero of Hyrule season pass, which bundles in four DLC packs for $20.