Flee

Fleeing describes the behavior of most NPCs when they reach low health (under 20% HP?). If the NPC regenerates above a threshold (30% HP?), they cease fleeing and resume normal behavior. This behavior is similar to the temporary effect of Fear and similar spells.

While fleeing, the NPC will begin pathing in a random direction, or in tight spaces, in a prescribed path. Sometimes the NPC may change directions. In open areas, NPCs will always change directions while fleeing if they reach a certain distance from the player. The effect of this is that a fleeing NPC will never run too far away, and should always be within visible range (though they may still be obscured by objects, terrain, or fog).

• NPCs with social aggro mechanics usually won't start fleeing if they are near other NPCs of the same primary faction. {Perhaps to avoid appearing a coward before their peers). They won't stop fleeing if they come within range, however. Use this to your advantage in areas where fleeing enemies are dangerous such as densely packed dungeons. Feared NPCs ignore this rule.
• Fleeing NPCs at very low health will move more slowly, until the point of almost stopping.
• Snare has no direct effect on NPC behavior, but it can further reduce movement speed to zero.
• Rooted NPCs always exhibit rooted behavior over flee or fear behavior, and resume such behavior when root breaks. Though NPCs will fight back against melee players while rooted, this is sometimes preferable in dangerous environments such as densely packed dungeons.
• Pets never flee. Undead enemies usually do not flee. Animals and humanoids usually do.