- Rules Compendium, page 200 Forced Movement: Movement that a creature is compelled to do, specifically a pull, a push or a slide. A creature can be moved in other ways, such as through teleportation, but only pulls, pushes and slides are technically forced movement.
- Rules Compendium, page 207 Hindering Terrain; Saving Throw: A creature can make a saving throw to avoid being forced into hindering terrain, whether it is pulled, pushed, slid, teleported or otherwised moved against its will.
- Rules Compendium, pages 212-213 Forced Movement; Catching Oneself If a target is forced … into hindering terrain, …, the target can immediately make a saving throw to avoid going over the edge or entering that terrain. If the creature saves, it falls prone in the last square it occupied before it would have fallen or entered the terrain. … Once the saving throw is resolved, the forced movement ends.
Forced Movement into hindering terrain
If a forced movement power would move a creature extra squares into hindering terrain, the extra squares of movement can be applied as a penalty to the creature’s saving throw. Thus, if a creature is at the edge of a cliff and you push it three squares, you can push it one square (off the cliff) and give the creature a -2 penalty to the saving throw to avoid going over the edge (so it needs a 12 or better to save itself).