According to the epic, the mother-Earth cannot support the weight of Svyatogor, but he can not overcome the "pull of the earth" contained in the bag; when he tries to lift the bag, his feet sink into the ground.
Svyatogor's father is "dark", he is blind - a sign of coming from another world.
After becoming a bogatyr of knyaz Vladimir the Bright Sun (Владимир Красное Солнышко, Vladimir Krasnoye Solnyshko), Ilya (another bogatyr) rides off to challenge Svyatogor, despite being forewarned not to do so by pilgrims who had miraculously healed him.
Ilya manages to lie down in the coffin first, but it appears too large for him, but it fits Svyatogor perfectly.
Before the coffin seals completely, Svyatogor passes part of his strength to Ilya through his breath.