Complex sentence: Instead of reviewing music videos, they reviewed (custom-made) pages from other Marvel Comics--in one with Ghost Rider, Beavis tries to avoid using the word "fire" to describe the character's fiery skull.
Split into simpler sentences: Instead of reviewing music videos, they reviewed (custom-made) pages from other Marvel Comics. In their review of a Ghost Rider comic, Beavis tries to avoid using the word "fire" to describe the character's fiery skull.