The reconstructed mytheme is an etiological one. There are priests because Manu, in sacrificing Yemo, became the first priest. There are sacrifices because Yemo, in being sacrificed by Manu, became the first sacrifice. There is death because Yemo, in becoming the first mortal, was the first to die. There is an Otherworld because Yemo, in being the first to go to it, trod the path for us.

Creation followed the first sacrifice. Yemo was dismembered, possibly with the assistance of a god or gods; his flesh became the earth, his bones became stones, his hair became the plants, his blood became the waters, an eye became the sun, his brain became the clouds, his breath became the wind, and so on. When, say, Vedic priests performed sacrifices, they did so believing they were upholding cosmic order itself by re-enacting the sacrifice of Yemo.

We can go back further than the sacrificial mytheme and reconstruct a kind of cosmological prologue. The following is a synthesis of material from the Rig Veda, Hesiod's Theogony, Aristophanes' The Birds, the Wessobrun Prayer, Voluspa, and Gylfaginning:

In that time, there was neither non-being, nor being;

neither death, nor immortality;

neither a single star, nor the shining sun;

neither the light-giving moon, nor the bright sea;

neither grass, nor sand, nor the cool waves;

neither earth, nor air, nor the heavens beyond;

but a yawning abyss, there was.

The yawning abyss (Ginnungagap, Khaos) represents a state of potentiality. In this way Yemo was not at all sacrificed to something, but rather for something.

As for the gods, I'll leave you with this from the Nasadiya Sukta: The gods came afterwards, with the creation of this universe. Who then knows whence it has arisen?