'Tis the vault of thy lost Ulalume!" (line 81)
The death of Ulalume is what has been tormenting our poor speaker, even though we don't know about it until this line. If this poem is a bit of a mystery, then this line gives us the solution. Of course, if you've read other Poe works, like "The Raven," then maybe you weren't too surprised by this. Like we said earlier, there's a pretty heavy death vibe all throughout this poem.
That I brought a dread burden down here— (line 88)
We just love the phrase "dread burden." We think it does a really brilliant job of evoking the suffering the speaker must be enduring. The pain of remembering Ulalume is like a weight on this whole poem. The speaker doesn't ever even refer to her death directly. He just gives us this hint about a mysterious "burden." The terrible heaviness of Ulalume's corpse is all the more horrifying because we're left to imagine it for ourselves.