The Elegiast /
The Ivory Dove
'We call upon the Elegiast,
who calls each of the Dead by name;
who cannot be deceived;
from whom nothing more can be taken' 
The Elegiast is an Hour which commemorates and grieves, heavily associated with memory, loss, and death. While not the kindest of the Hours, he is never cruel, and remembers all his promises. He is the power which prevents the world from forgetting the lost Hours. His aspect is Winter and his hour is 9 a.m.
The Lithomachy: While the Elegiast did not take part in the Lithomachy, he now carries the memory of the dead god-from-stones, as well as the memory of the world before their death, for the Dove remembers when all others forget.
The Ordo Limiae: Also known as the House of Lethe, and later the Obliviates, the Ordo Limiae was an order of Long who hid themselves from the world and swore an oath to stay out of the affairs of the Hours. They apparently had an understanding with the Elegiast though, who they invoked during burial rites to prevent the souls of dead Long from falling into the hands of the Hours.
The Roost: As the Ivory Dove, the Elegiast is counted among the aviform Hours, who meet at a secret location called the Roost. There, they share rumours and gossip with one another, though they look unkindly upon mortals who overhear them. The location of the Roost changes upon discovery, but was originally in Miah, and later hidden in the mountains north of Gordion.
- Miss Naenia: The gentlest of the Elegiast’s Names, who can be encountered both in the Dancer legacy and, more prominently, in the Ghoul legacy, where she inhabits a painting bearing her name and guides the player on their path of Remembrance. She is described as a “dark-skinned woman with snow-coloured eyes and close-cropped ivory-coloured hair.
- The Beachcomber, the Vagabond, the Twins: The other aviform hours which the Elegiast meets with at the Roost.
- The Elegiast has a role in the Heart path of the Change ascension, where the player’s Sending takes the form of a dove and travels to Port Noon to learn the lesson, “Bones, Surrendered”.
- The Ghoul legacy heavily revolves around the Elegiast, as the player gathers the memories of lost colours for the Palest Painting, using the Elixir Zeboim to draw them from the flesh of the dead. It is implied that player is not the first to attempt such an endeavour.
- The Elegiast's single-Winter is confirmed by AK.
Real World References
- The Elegiast takes the place of the Hermit in the Tarot of the Hours. The Hermit can represent contemplation, solitude, and prudence, as well as marking a period of soul-searching and self-reflection.
- Miss Naenia is named after a Roman funeral deity, Nenia Dea, a personification of a funerary lament’s protective power. Curiously, in some accounts she is associated with Janus, in his role as the two-faced god of beginnings and gateways at birth contrasted to her as a goddess of endings upon death.
- As hinted by the AK's answer about the Ivory Dove's origin (‘Iona’), he is likely inspired at least in part by the author of the Book of Iona (also known as the Book of Kells) - St. Columba/Colm Cille (literally 'dove'/'church dove' in Latin/Irish), an early-medieval Christian saint of Gaelic origin, who is known for his efforts at establishing a number of monasteries in Scotland and Ireland and at recording history (both directly or through descendant-monasteries). It's possible that he was an avatar or high-ranked servant of the Elegiast. In general, the Dove's influence can be noticed around the British Isles - a there's Hush House with strong remembrance affiliation, a secret library in Gwaer Inn, and St. Doves in Kerisham.
Theories and Questions
- The Elegiast is the only Hour from the standard Tarot whose origin is completely unknown. It is assumed that he is either a god-from-Blood or a good-from-Flesh, since the Horned Axe is the last god-from-Stone, the gods-from-Light are numbered and all accounted for, and the known gods-from-Nowhere all exist outside the standard Hour numbering system. One theory is that his birth is related to the Lithomachy, as an Hour whose purpose is to keep the world from forgetting the lost Hours, but apart from the vague tie to Iona, there is not much information to go on.
1. We call upon the Elegiast, who calls each of the Dead by name
We call upon the Elegiast, who cannot be deceived
We call upon the Elegiast, from whom nothing more can be taken
2. Invocation of the Ivory Dove
3. Until Winter
4. Read 'The World Does Not Weep'
5. Guise: Dove
6. Read 'The Ivory Book'
7. Read 'The Book of the White Cat'
8. Inaam, Kapigiginlupir, Garkie, Cryppys
9. Read 'In The Mountains As Upon The Plain...'
10. Guise: Eagle
11. The Elegiast's Name
12. 'Miss Naenia'
13. St. Columba
14. The White Library
15. The Lost Histories, enigma doc
16. Bones, Surrendered
17. The Palest Painting
18. Formula: Elixir Zeboim
19. Study 'On the White'
20. The Elegiast's Price
21. Source, original message