This property specifies which motions the AI uses; for example, a normal Sword Guard has 'WithSword 0', which makes the AI make sword guard style motions; for instance, the AI swings it's right arm as if holding a sword while attacking. A Hammerite, on the other hand, has 'Hammer 0, WithSword 0'. When attacking, the hammerite will use heavy swinging motions instead of quick jabs. Check the ActorTagList property of the original Thief AIs or check the TTLG Forums for a list of possible motions.
Property Name: MotActorTagList