OnDestroy Function ondestroyfn : Name of the function to use from already parsed .as script files when entity is destroyed (killed) in any way. If the function belongs to namespace, you must use prefix with the namespace name (e.g. mynamespace::MyFunction) for the keyvalue.

Name targetname : Set name of env_xenmaker so other entities can trigger it to spawn monster (if place available). Every trigger use-type works uniformly. Can be kill-targeted. Monster in queue (those who couldn't spawn because there was no room for them) won't spawn.

Target target : Name of entity to trigger (fire). Which function relates to it depends on the respective entity. Most will just trigger their target, while others will perform actions on their target or use it as a reference for other activities. Often, multiple entities by the same name may be targeted. Most entities need no target, but having one is essential for most logic entities and basic trigger-systems.

Pitch Yaw Roll (X Y Z) angles : Where Z means Y and Y means Z, that is, when you're thinking Hammer-grid. (Hammer uses Z for height and Y for depth, while every other sane 3D-application does this the other way round; nonetheless this keyvalue description has the letters in the conventional order) This, technically, is a 3D-vector containing Euler-angles to describe either the entity's rotation or direction of effect. E.g. a func_door_rotating will use this as its initial rotation, while a trigger_push will keep its original alignment and use this for the direction of its push-effect instead. Euler-angles are a hierarchical system to determine an object's orientation in 3D-space. A yaw-value of 0 would mean the entity would face east. (right in top-down view) 90 would mean it would face north. (up in top-down-view) After yaw, pitch is applied. Think aiming up/down with your character in first person. At last, the roll-value is applied. Think your character falling over sideways in first person. Some entities, mostly point entities, do not use the angles keyvalue for any purpose.