Simplify the following text for a Grade 4 native English-speaking person.
Original: The last meeting between the serpent and Thor is predicted to occur at RagnarÃ k , when JÃ rmungandr will come out of the ocean and poison the sky .
Simplified: JÃ rmungandr 's arch enemy is the god Thor . It is said that both Thor and JÃ rmungandr will die fighting each other during RagnarÃ k.