Elemental Manacles, Greater - These mithral manacles play host to a bound large earth elemental. These manacles behave in every way as a pair of mithral manacles with two magical exceptions.
First, if the manacles are thrown at and hit a small or medium target using a ranged touch attack, the elemental manacles will automatically attempt a grapple (CMB +16, CMD 25). If the Elemental Manacles successfully win the grapple, the binders clamp around targets wrists, trapping them. The victim is considered grappled until the manacles are removed. The Escape Artist check is a DC 40 (vs. a 35 for Masterwork), 15 hardness, 68 HP (as per the large earth elemental), and a break DC of 35. If the ranged touch attack misses or the initial grapple attempt fails, the charge is still spent. This ability uses one charge.
Using the second ability, the owner may command the earth elemental to engulf the person entrapped by the manacles. For 8 rounds (the HD of the large earth elemental), the elemental will attack and attempt to completely draw the victim into the ground where it will smother and crush them.
Starting on their initiative, the target gets a DC 17 (Str-based) Reflex save each round to avoid being engulfed. This is a standard action. Once the target is engulfed, the elemental automatically does 2d6+7 crushing damage to the target and the target is pinned for the remainder of the 8 rounds. Each round the target is engulfed, he may make an opposed grapple check (see stats above). If the target wins the opposed check, he is not considered pinned for that round, but still takes damage. He must continue to make the opposed grapple check for the remainder of the 8 rounds to avoid becoming pinned again. This ability uses two charges.
Elemental Manacles, Lesser - These masterwork manacles behave very similar to the greater version, except there is a medium-sized earth elemental bound to these. The CMB is +9, CMD 18, Escape Artist check is 35, Break check DC is 28, they have a 10 hardness and 34 hit points. The lesser elemental manacles do not gain the engulf ability.
Both the greater and the lesser have 3 charges per day.
Lesser - Craft Wonderous Item, Bind Elemental (Feat), Lesser Planar Binding, Cost: 9,000
Greater - Craft Wonderous Item, Bind Elemental (Feat), Greater Planar Binding, Cost: 36,000
NOTE: Elemental Manacles is based upon the creation feat conversion of Bind Elemental for Eberron. This feat and creation process can easily be adapted into your campaign by removing the Khyber Dragonshard requirement and placing a standard Pathfinder gem type of the same value in its place.