House rules are small fan created additions and replacements to core rules in a rules set. In most cases, they are not officially sanctioned by the designer, in contrast to optional rules. For substantial new material and rules subsystems, use the [homebrew] tag instead.
This spell from page 104 the Dungeons and Dragons, 3rd Edition supplement Book of Vile Darkness--even more than the spell consume likeness--makes my head hurt. I'd just let it go and find a different ...