The Erinyes devil has the extraordinary ability to Entangle an opponent, it reads:
Each erinyes carries a stout rope some 50 feet long that entangles opponents of any size as an animate rope spell (caster level 16th). An erinyes can hurl its rope 30 feet with no range penalty.
However, the entry is not specific about the type and properties of the rope (
some 50 feet long are hardly very specific) and I could totally imagine a devil with a fondness for tying up its victims to not use a standard piece of rope. Probably it would use a 2 inch diameter rope of 50 feet or a 3 inch diameter rope of 32 feet, or maybe even a piece of rare bloodvine rope. Now, such ropes could be animated by a 16th level caster like the Erinyes, but the Animate Rope spell assumes a standard 1 inch diameter piece of hempen rope is used.. How would hit points, break DC, escape artist DC and spellcasting Concentration DC change for ropes of different diameter or for bloodvine rope when used for Animate Rope?