Some of the new creatures on Panda's blog get this "Special Maneuver":
Hamstring: The creature may spend an additional success from an Attack test to halve the opponent’s Movement until the end of the next round. If the attack causes a Wound, the reduction lasts until the Wound is healed.
This is mirrored by one of the 3E optional combat rules:
DAMAGED LIMB TABLE (Excellent Success vs WT)
Leg | The character suffers a –1 penalty to Action Tests requiring use of the damaged leg. The character’s Movement Rate is halved.
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So, I'd convert this to a Called Shot Rule: A Called Shot targeting a Leg and that causes a Wound halves the opponent’s Movement until the Wound is healed.
Dire Wolves and those with the Hamstring ability can cause a 2 round penalty if they do not cause a Wound.
Now the Dire Rat has a great motivation to start chewing the Elf's legs up, especially if you give them Hamstring. Get both legs and he's only running 3-4 yards per round!
