>1. Costoboci was a Dacian Tribe not a Sarmatian one...
> This is my current view on this grouping.
> Known since ca. the 2nd c BCE (if that is the correct date for Pliny's source at NH 6.19, which seems plausible), but not mentioned afaik in any extant text before ca 75 CE. Originally a Sarmatian tribe on the Don, "beyond" the classical Sarmatians of Herodotus. Probably Aorsan. Located northeast of the Carpathians by Ptolemy (north of the Bastarnae) (Geogr. 3.5). Perhaps by then (ca. 114 CE if from Marinus) the name was already that of a polyethnic association or confederation, with Germanic, Venedic, Dacian, and Sarmatian elements. Since it was designated by the original Sarmatian (Aorsan?) name, it seems reasonable to assume that it was formed under Sarmatian hegemony, probably near the mid-first century CE, when King Farzoi was building his empire. But as Ptolemy distinguishes the Costoboci from the Transmontani (Dacians?) and Igylliones (Przeworsk-Zarubinians?) this confederation might in fact have been a short-lived post-Farzoi clan dominance
> phenomenon in West Ukraine. Archaeological data indicate that the Sarmatian element was at least three-pronged (Aorsans of the Farzoi and Inismei clans, Costoboci, and Yazigi), if not even more complex (the political appurtenance of Pliny's "Sardi Scythae" and "Siraki" being unclear). The numerically dominant Germanic element (judging by discovered sites) was represented by the eastern Przeworsk culture, and by the Zarubinians migrating southward from Polissia (the latter would also have included Venedi). The Lypytsia component was Dacian. As time went on the various groups began to fuse, and for the period ca. 100-250 CE Ukrainian archaeologists speak of the common "Zubrytska" culture, with input from all ethna, but with predominantly Zarubinian and Przeworsk characteristics. The Costoboci entered the historical mainstream briefly in the 170's, when they invaded the Roman Empire (Pausanias; Cassius Dio). They were beaten back, and within a year or two
> were conquered by the Asding Vandals (there is archaeological evidence for this). We know very little of their political organization in the 1rst/2nd cs. CE. Possibly the ethnic components retained much autonomy. The only Costobocan "king" (rex Costobociensis) we know of (from a Roman inscription) was one Pieporus, almost certainly of the Dacian group. It is possible, though not, however, certain, that "rex Costobociensis"= "rex Costobocorum", and that Pieporus was an overall sovereign of the Costoboci, though he might equally plausibly have been a "rex" of the Lypytsia people. The Vandal-dominated ex-Costobocan territory was eventually incorporated into the Black Sea Gothic association. It retained certain archaeeological specificities within the Chernyakhiv culture. Most of this population migrated southwestward in the wake of the Hunnic onslaught. The remnant was subsequently slavicized.