Benefit: An opponent damaged by the slayer‘s sneak attack has its speed halved for 1d4 rounds. A successful Fortitude saving throw negates this effect (DC = 10 + 1/2 of the slayer’s level + the slayer’s Intelligence modifier). Against creatures with multiple types of movement, the slayer must choose which movement type to affect. If the slayer affects a creature’s flight movement, its maneuverability is reduced by one step; if it’s airborne at the time, it falls unless it succeeds at a DC 10 Fly check. If the slayer targets a creature already affected by this ability, its speed and maneuverability are not further reduced; the slayer may either extend the duration of that effect by 1d4 rounds or choose another movement type to affect (keeping track of the duration of each affected movement separately).
Pathfinder Roleplaying Game: Advanced Class Guide