The scene depicts an offering being made by Horus Bedhety or as Ihy, referring to his aspect as a sistrum player, to the goddess Hathor (who in later evolutions of mythology is his mother) seated before a giant menat necklace.
He is presenting a sistrum, bearing the face of Hathor just like those on the menat necklace. To the left - and enlarged in typical style to simply fill available space - is the counterweight which hung down a person's back, connected by four beaded strings to the necklace.
If you look closely at the seated figure of Hathor, you will notice that she too wears such a menat necklace.
Between two of the sistrums on the giant necklace, a solar barque can be seen.
This relief is not a scene depicting a myth or a legend, Will.
It is an offering scene which features Hathor prominently because the temple at Dendera was erected in her name. The idea of Hathor being the mother of Horus attests to the idea of this relief being very late, associated with the Ptolemaic dynasty (305 BC to 30 BC, so not really what we consider 'Ancient Egyptian.')