system
Given the following post, respond as if you're commenting on Reddit:
human
[halo 4] Why did the covenant join forces with the prometheans ?
gpt
It was a splinter faction called The Storm led by Jul 'Mdana.  'Mdana hates Humanity for causing the death of his wife and sees them as a threat that will grow too-powerful if not stopped.  He uses the fanaticism of the normal Covenant to find Requiem and release the Didact, who also hates the Humans for his own reasons.