Learn English – Synonym for vicious circle but without the negative flavour

Yes: abyss, as in "abyssal depths" of the ocean. That's neutral and simply means "very very deep".

The infinite negativity of Hell is the Abyss with a capital A and (generally) the definite article.

The conventional term for this is unsignatured.

unsignatured — adj. * * * unˈsignatured, ppl. a. (un 1 8.) Brydges Censura Lit. III. 342 Such notes..as appear unsignatured at the bottom of the page.

signature 2. Base verb from the following inflections: signaturing, signatured, signatures, signaturer, signaturers, signaturingly and signaturedly

Also consider:
sig·na·ture·less, adjective

Usage examples from different contexts:

d) Unsignatured ELT Signals The existing 121.5/243 MHz signals are unsignatured, i.e., they do not at present carry any form of unique identifying code to enable the LUT to separate the frequency ... (Intl. Elec. Elecs. Conf. Proc.)

Signatured parts tend to occupy a pitch-range roughly a fifth lower (for one flat) than unsignatured upper parts in the same pieces, … (Music)