Commander Lilith & the Fight for Sanctuary was an expansion for Borderlands 2 released in June of 2019 as a way of hyping up the release of Borderlands 3. It boosted the level cap to 80, added the option to start a new character at level 30 and skip the tutorial (hallelujah), threw in a new tier of weapons, and mainly just let you hang out with your favorite characters again while shooting up a slightly different variety of bad dudes.
It was free for its first month on Steam, and now it's free again on the Epic Games Store. Which is nice, because it's the one DLC that isn't bundled in with the Borderlands Handsome Collection they gave away for free in May. You've got until October 2 to add it to your account.
Commander Lilith & the Fight for Sanctuary is a pretty good piece of DLC and it's hard to argue with the price, but it's not up there with the five essential Borderlands DLC expansions you should definitely play.