In addition to physically breaking away by force, eradicating mirages involved the ability to distinguish it as an illusionary world with your wisdom and destroy the conflicts of Laws in the Spectral World.
Grimm was certain that he had fallen into some unknown spectral world while suffering a minor memory loss.
Despite the loss of memory, his subconscious, or rather his sixth sense, told him that something had happened to him beforehand, he simply forgot what it was.
It was like when you woke up the next day, trying to remember the obscure dream the night before but had forgotten the contents of the dream.
"Argh…"