Retreat

Retreating is a mechanic used by NPCs to primarily escape from combat. A version of retreating can be seen when shooing the stray dog in Varrock, causing it to retreat seven game squares away from the player.

Conditions

The mechanic will generally be executed under two circumstances:

• The NPC gets attacked from outside their Max Range.
• The NPC’s hitpoints fall below a certain threshold. This only applies to select few NPCs, such as imps and chickens.

The mechanic will halt under the following circumstances:

• The NPC can no longer retreat in the given direction and at least one of the two sides of the direction in which the NPC is retreating contains a wall. If the NPC retreats to a position in which it can no longer go any further(due to the Max Range restrictions), but isn’t blocked by anything that would prevent movement in either of the directions of the retreat direction(E.G. if the NPC retreats South-West, meaning neither the South direction nor the West direction contains anything that would otherwise block the movement), the NPC will continue trying to retreat.
• The Chebyshev distance between the NPC and whom it is retreating from is greater than 25 game tiles.
• The NPC gets interrupted by something else, such as a player attacking it.

Retreat Directions

An NPC will always retreat away in a specific direction in relation to whom it’s retreating from. The below table shows the direction in which an NPC will retreat:

The entity position denotes the position at which the entity from whom the NPC is retreating from is standing at.

The generation of the direction can be achieved using this code block:

val retreatDirection = when {
    target.x >= this.x && target.y >= this.y -> Direction.SouthWest
    target.x >= this.x && target.y < this.y -> Direction.NorthWest
    target.x < this.x && target.y >= this.y -> Direction.SouthEast
    else -> Direction.NorthEast
}

The target stands for the entity from whom the NPC is retreating, whereas this refers to the NPC who is retreating.

Media

The above video demonstrates attacking an NPC, moving outside its Max Range, then attacking it to cause it to retreat. The NPC then begins retreating, actively re-calculating the path it’s taking in relation to the target. The gif ends with the NPC moving up against the wall, thus halting the retreating.