Which Anglo-Saxon epic poem features Grendel?

Beowulf, which survives in exactly one manuscript - and that manuscript was in a fire in 1731 that destroyed part of the library holding it. The edges were charred and crumbled for decades afterwards, so words at the margins have been lost since the first transcriptions were made, which are now evidence in their own right.

It is set in Scandinavia, not England, and is about Geats and Danes - so the founding poem of English literature concerns other people, in another country, written in a language modern English speakers cannot read without training. It is also Christian in framing and pagan in material, which suggests a poet working over older stories.

Its critical reputation was rescued by Tolkien. Scholars had treated it mainly as a source of historical and linguistic evidence, faintly embarrassed by the monsters; his 1936 lecture argued that the monsters are the point, that it is a poem about mortality and the certainty of defeat rather than a defective epic. That argument won, and modern Beowulf criticism starts from it. Seamus Heaney's 1999 translation then made it a bestseller, which almost no scholarly poem manages.