"The Dark Château" by Clark Ashton Smith

Tons of good vocabulary packed into this poem!

Acherontic: dark and dismal (as of the river Acheron in Hades)

attar: a fragrant essential oil (as from rose petals)

oriel: a large bay window projecting from a wall and supported by a corbel or bracket

gules: the heraldric term for red

verdure: the greenness of growing vegetation; health and vigor

oleander: a poisonous evergreen shrub (Nerium oleander) of the dogbane family with clusters of fragrant white to red flowers

hoar: this word has several definitions that could fit the bill here, so you can pick whichever one tickles your fancy the most: frosty; ancient; no longer interesting or meaningful due to repetition over time

seneschal: the steward or major-domo of a medieval great house

coigne: given the association with 'niche', we're probably looking at the meaning of "a projecting corner", but it could also mean "the keystone of an arch", or " the external corner of a building; especially any of the large, squared stones by which the corner of a building is marked", or any wedgelike piece of stone. Anyways, you get the idea.

jambart (or jambeau): a greave, i.e. a piece of armour worn to protect the shin from the ankle to the knee

lampadephore: torch bearer. Or I suppose in this case, lamp bearer.

limn: the draw or paint on a surface. Or possible: to outline in clear sharp detail. Not entirely clear which definition fits better.

The picture used is "The Dark Chateau" (1919) by Leslie Moffat Ward. Frankly it reminds me strongly of "The Fall of the House of Usher", but it'll have to do for here.

To follow along: http://www.eldritchdark.com/writings/poetry/113/the-dark-chateau