Stentoriphonically

Meaning: loudly; as if through a speaking-trumpet, or stentorophonic horn.

Usefulness: 2 (It's a bit of a mouthful, but useful if you're after something elaborate. Stentorophonic horn is rather useful as a more interesting name for hearing aids.)

Logofascination: 1 (In 1671 Sir Samuel Morland - academic, diplomat, spy, inventor and mathematician* - claims to have invented what we would call a megaphone, but he called the stentorophonic horn. Stentoriphonically appears in G&P Le Tiers-Livre in 1693, but Sir Thomas had died in 1660; this may be one of Motteux's sneaking in. Sir Thomas might well have made an allusion to Stentor, mythical source for this and stentorian, but the suffix -phonic is not quite right.**)

In the wild: No.

Mezentian

Meaning: resembling Mezentius, an Etruscan king exiled for cruelty (according to Virgil, anyway).

Usefulness: 1 ("An early meeting the day after a long weekend? A Mezentian idea!")

Logofascination: 1 (The OED has three citations between 1798 and 1874. The next is 1992, from Iain Banks' Crow Road. Between Iain and Iain M. Banks, the late, lamented author has 136 citations in the OED, a number of them to do with whisky. Sadly, my favourite of his books, Transition,  seems to have been lexicographically neglected by the OED. If you're interested, the list of the words with Iain / Iain M. Banks citations is at the end of the post.)

In the wild: Crow Road: "It did occur to me he could have driven the bike himself with the body lashed to his back looking like a pillion. It's a bit Mezentian, but possible."