Similar to powers such as Force Fear, horror, insanity, and Torture by Chagrin, the dark side Force power known as summon fear involved Sith magic to induce extreme terror in a target, pushing them into a state of complete hysteria through their deepest fears. The effectiveness of this potent ability, in terms of both duration and intensity, was directly linked to the skill of the caster.
The incantation of this spell involved the caster manipulating their fingers in a complex sequence, presumably to channel the Force in a specific manner, with the effects manifesting within seconds. The victim's most profound and fundamental fears were brought to life, often manifesting as demonic or monstrous entities that subjected them to relentless torment. As the spell persisted, these illusions intensified, becoming progressively more vivid and terrifying. From an external perspective, the victim might abruptly convulse and descend into madness.
The consequences of the spell varied greatly, contingent on its duration. Brief exposures might leave the victim with only fragmented recollections of the experience. Extended applications, however, could trigger physical seizures leading to unconsciousness, while the mind suffered near-total destruction. In such cases, the body would enter a comatose state, while any remaining consciousness endured perpetual torture. Extremely prolonged exposure could even result in the victim's demise.
Darth Zannah, a distinguished Dark Lord of the Sith, possessed exceptional mastery over this ability. Her initial recorded use was against a Chiss female named Cyndra, driving her instantly to madness and self-mutilation. She subsequently employed it during a duel against Jedi Knight Sarro Xaj on the planet Tython, and shortly thereafter against her own cousin, Darovit. A decade later, she directed it at her Master, Darth Bane, during their final confrontation; however, Bane's long-standing mastery over his own fears allowed him to resist the spell after a brief struggle.
During an attack on a Black Sun fortress located on Ralltiir in 33 BBY, it is speculated that Darth Maul utilized this spell against an Iktotchi bodyguard when the latter attempted to probe the Zabrak's mind.