There are some Ghost-type enemies with unique names or that can only be encountered during special events.
See main article: Scarecrow.
Onryou (怨霊, "vengeful spirit") is an alternate Ghost in the Assassin version of the 40 AP GUDAGUDA Honnouji Event daily quest. It has the skill Grudge (怨念) that drains one friendly Servant's NP gauge by 10%. Onryou has a NP gauge of 3 and can act up to two times per turn.
The Captivating Onryou (艶めかしい怨霊) is a midboss Ghost in the Assassin version of the 40 AP GUDAGUDA Honnouji Event daily quest. It has the skill かなしばり, which paralyze one friendly Servant for 1 turn; the skill name may refer to "金縛り," which means "sleep paralysis," but it could also be a play on the words "悲しい" (sorrow, grief) and "縛り" (binding, bondage). Its Noble Phantasm, Possession (ポゼッション), charges with 3 ticks and deals high damage while also afflicting NP Seal for 1 turn. Captivating Onryou can act three times per turn.
Void (無間) is a memorable Ghost encounter in the Kara no Kyoukai Collaboration Event. In the Woods is a special quest that forces Ryougi Shiki (Saber) as the support Servant. The quest is simply 3 Voids with 6,666,666 HP. They have long Charge Gauges, but also constantly cast 10,000 HP AOE heals. To beat the quest, you must charge up Ryougi Shiki (Saber)'s Noble Phantasm, use her Mystic Eyes of Death Perception skill, then use her NP. This should instantly kill all 3 Voids