Phantasm:

phantasm (n.): the mental imagery produced by fantasy; (adj.): phantasmal, phantasmical; (adv.): *phantasmically*. [Greek phantasma, ‘an appearance’]. [emphasis added]. ~ (Farlex Partner Medical Dictionary).

Phantasmagorically:

phantasmagorically (adv.): in a phantasmagoric manner; [e.g.]: “Yet the realist vision shifts to the phantasmagoric, as spectator and spectacle undergo carnivalesque reversals and interpenetration”; “the story enters a more phantasmagoric world, and nightmarish and unreal events seem to occur”; see phantasmagoria; viz.: phantasmagoria (n.): as in a sequence of real or imaginary images like that seen in a dream; [e.g.]: “Mere words could never capture the phantasmagoria of our dreamscape”; “someone had set up a strobe light in the back, so the dancing figures were in silhouette, and their movements appeared to consist of a series of slides; like the images from a phantasmagoria”; (synonyms): delusion, illusion, figment of the imagination, vision, apparition, mirage, chimera, fantasy, dream, daydream; (adj.): phantasmagorial; (n.): phantasmagorist. [origin: Mid 19th century; earliest use found in novelist Sylvester Judd (1813-1853); from phantasmagorical + -ly; from phantasmagoria; originally the name of a London exhibition (1802) of optical illusions produced chiefly by magic lantern: probably from French fantasmagorie, from fantasme, ‘phantasm’ + a fanciful suffix]. ~ (Oxford English Dictionary).

Phantasmal:

• phantasmal (adj.): relating to or of the nature of a phantasm[†]; unsubstantial; apparitional; imaginary; illusive, phantasmic; phantasmical; (adv.): phantasmally, phantasmically. ~ (Funk & Wagnalls Dictionary).

[†]phantasm (n.): an imaginary appearance; a phantom[⁑]; fancy; ~ (Funk & Wagnalls Dictionary).

[⁑]phantom (n.): something that exists only in appearance; an apparition; a ghost; spectre; a vision; an illusion; mirage; often used adjectively; as, “a phantom ship”. ~ (Funk & Wagnalls Dictionary).

[www.funkandwagnalls.com/phantasmal].

• phantasmal (adj.): of, relating to, or in the nature of an illusion; lacking reality: chimeric, chimerical, delusive, delusory, dreamlike, hallucinatory, illusive, illusory, phantasmagoric, phantasmic, visionary. ~ (American Heritage Roget’s Thesaurus).

Phantasmicality:

phantasmicality (n.): of, resembling or characteristic of a phantasma (=not existing in nature or subject to explanation according to natural laws; not physical or material); [e.g.]: “Thus, the phantasmicality of the spirit in an apparent-body has become quite solid and popular once again”. (page 57⁽⁰¹⁾, “The Unique and Its Property”, by Max Stirner; translated 2017, Underworld Amusements, Baltimore (first published in 1844; lit. ‘The Individual and His Property’, by Johann Kaspar Schmidt, 1806-1856⁽⁰²⁾). [circa 1200; Middle English fantesme, from Old French from Latin phantasma, from Greek phántasma, ‘image’, ‘vision’]. ~ (Online Neoteric Dictionary).
⁽⁰¹⁾ [https://archive.org/details/StirnerTheUniqueAndItsProperty/page/n57/mode/1up].
⁽⁰²⁾ [https://en.wikipedia.org/wiki/The_Ego_and_Its_Own].