Custom delay before first strike - delay in seconds before the first mortar strike in sequence of strikes. If omitted or 0, the default value 2.5 is used.
Don't set activator as attacker - the activator of the func_mortar_field won’t be used as an attacker for mortar strikes. By default the activator is sent as an attacker. E.g. even if player activated the func_mortar_field via trigger_once, the mortar strikes will be attributed to the player, thus making monsters who were damaged by the strike think that they have been attacked by the player. Use this flag to prevent such behavior if it’s undesired. As an alternative you can also put the trigger_relay between the calling trigger and the func_mortar_field to ensure the original activator (usually the player) is not used.
Mortar.Beam - the beam visual representing the trail effect of the mortar strike (from top to bottom).
Mortar.Circle - the cicle beam visual representing the shock wave from the impact. The sprite for this visual is not defined by default, thus the wave doesn’t appear unless the sprite is defined. The rest of parameters use the values left by Valve in the code that was disabled (they might have been thinking the effect doesn’t fit, but you can give it a try).