Unfortunately, it turned out that Adsullata was Adsalluta. She and her partner, Savus, are unusual in that they are a divine couple who retained their native names, with no Roman overlay. (The Epigraph Databank has eight entries for Adsalluta, seven for Savus, but none for Adsullata.)
You have probably never heard of either one, and that’s not surprising. Although they seem to have been important locally, with a sanctuary on a dangerous bend of the river Sava in Slovenia, they aren’t generally known.
Adsalluta was a Celtic deity, worshipped by the Taurisci. The god Savus was a personification of his river, and shared its name; both of them looked after the safety of the merchants and travellers who used the river, as well as those who piloted them through the rapids below their sanctuary near Podkraj.
The river Savus connected Italy to the Danube, and ultimately it formed a small part of the amber route. The river also achieved literary fame in the story of the Argonauts: as they were returning from Colchis with the Golden Fleece, they travelled along the Savus on their way to the Adriatic Sea.
There are a number of altars and sanctuaries to the Roman god Neptune and the Nymphs (water-spirits) along the river, but this particular bend was reserved for the local deities, presumably on the grounds that it would be unwise to offend or replace them. Neptune’s altar stood across the river from Adsalluata and Savus’, a graceful compromise. (Savus also appeared on Roman coins along with the god Colapis, whose river joined the Savus at Siscia.)
There were two reasons to give thanks for safe passage: 1) the sanctuary was just below some dangerous rapids, and 2) in summer the water could become very low, making travel impossible.
Travellers did feel grateful to them: ten altars, nine to the two deities (5) or Adsalluta alone (4), along with one with no inscription, were found near the Roman town of Celeia, now Celje. (Adsalluta seems to have been purely local, but inscriptions to Savus have turned up in two other places along the river: an altar at Vernek in Roman Emona, and a curse tablet at Siscia, as well as an altar found near Scitarjevo in Croatia.
The people who dedicated the altars seem to be a mix of locals and Romans. The latter were mainly merchant families, with roots in northern Italy.
Savus and Cursing
The curse tablet makes a link to Sulis, as they were also found at her temple. (Not that they were the only deities ever invoked on curse tablets. Defixiones in Britian alone invoked the local god Nodens, as well as Jupiter, Mercury and Mars, to curse enemies or wrong-doers.)
The Savus curse-tablet seems to be tailored to his watery nature:
You will give a command to Savus to see to it that he pulls them downwards, that they become speechless, that they cannot say or do anything against us…
Presumably to “pull down” means to drown them, or to render them similarly helpless. Savus would seem to have more to him than just protecting water traffic. (Both Nemesis and Savus had altars in the Roman town of Andautonia; perhaps they had more in common than we think.)
Salus and Adsalluta
A more concrete link to Sulis is the possible thermal springs near Adsalluta’s sanctuary. There are no springs there now, but they do appear and disappear throughout that region, and many had shrines devoted to the Nymphs, as well as the goddess Salus, or Health. The heavy woods around the site of her sanctuary could also have been a grove, which would be the Celtic site of worship until Roman times.
“Creative mishearing” may have helped Adsalluta if she did have hot springs, as her name does sound like Salus, and so would promote the health-giving virtues of her waters. All this is speculative, however.
Another altar, to the Roman goddess Magna Mater, has also been found at Adsalluta’s shrine. The cult of the Great Mother turned up alongside other Celtic goddesses associated with healing water, such as Sirona and Diana Mattiaca, which lends colour to the idea that Adsalluta had a sacred spring of her own.
As is often the case with these obscure deities, we have very little to work with. Obviously Adsalluta and Savus were protective deities, who looked after the river Savus and those who travelled on it. Beyond that, Adsalluta may have been a healing goddess, and Savus may have had some link with justice or retribution, but it’s hard to tell.
Alfoldy, Geza 2014: Noriucm (Routledge Revivals), Routledge. (Google Books)
Gregoratti, Leonardo 2013: “North Italic Settlers Along the Amber Route, Studia Antiqua et Archaeologica XIX: 133-153 (pdf here)
Green, William McAllen 1927: “Notes on the Augustan Deities.” The Classical Journal 23, no. 2 (1927): 86-93. (JSTOR)
Knevzovic, Ivan 2010: “The Worsip of Savus and Nemesis in Andautonia,” Arhekoloski vestnik 61: 187-202. (pdf here)
Kos, Marjeta Sasel 2010: “Adsalluta and Magna Mater – Is there a link?” Celtic Religion Across Space and Time, ed. J. Alberto Arenas-Esteban, Junta de Comunicadades de Castilla-La Mancha: 242-57. (academica.edu)
Kos, Marjeta Sasel 1994: “Adsalluta and Savus,” Arhekoloski vestnik 45: 99-122. (Google cache version)
Teichner, Felix 2013: “From Aqvileia to Carnvntvm: Georgraphical Mobility Along the Amber Road,” Veleia 30: 47-73. (pdf here)