Feral is going to make a Disarm attempt vs. Paladin. She is going to Power Attack for -5 to hit to get +5 to her Opposed check vs. Paladin's Strength if she hits ...
You first make an attack roll vs. Opponent's Parry for melee. She has Improved Disarm so no penalty to this roll. If she hits, she makes an Opposed check using her Damage vs. Paladin's Strength. If she wins she disarmed Paladin, forcing him to drop one held item (his hammer). If she is unarmed (she is) she can instead grab the hammer. As she has Improved Disarm, if she fails, you can try and disarm her (but she is not holding anything so)
Feral [roll0] vs. Paladin's Parry DEF 18
IF she succeeds, [roll1] vs. Paladin's Strength roll...