Question: What form of armored heavy cavalry used in ancient warfare did Grivpanvar fought?

full_context: Document 1: Cataphract: A cataphract was a form of armored heavy cavalry used in ancient warfare by a number of peoples in Western Eurasia and the Eurasian Steppe.
Document 2: SCA armoured combat: SCA armoured combat, or informally heavy combat, is a combat sport developed by the Society for Creative Anachronism (SCA) in which participants in protective body armour either "act out" mock combats loosely inspired by forms of historical combat practiced in medieval Europe or under supervision, may approximate historically real combat using SCA approved safe weapons under the watch of marshals to maintain safety. It is variously considered a combat sport, contact sport, or a form of martial art.
Document 3: Immortals (Achaemenid Empire): The Immortals (from the Greek Ἀθάνατοι "Athánatoi") also known as the Persian Immortals or Persian Warriors was the name given by Herodotus to an elite heavily-armed infantry unit of 10,000 soldiers in the army of the Achaemenid Empire. This force performed the dual roles of both Imperial Guard and standing army. The force consisted mainly of Persians, but also included Medes and Elamites. Essential questions regarding the unit (even its native name) remain unanswered, because authentic sources are missing.
Document 4: Sagittarii: Sagittarii (Latin, plural form of "Sagittarius") is the Latin term for archers. The term "sagittariorum" in the title of an infantry or cavalry unit indicated a specialized archer regiment. Regular auxiliary units of foot and horse archers appeared in the Roman army during the early empire. During the Principate roughly two thirds of all archers were on foot and one third were horse archers. Mercenary foot archers already served with the Roman republican army, but horse archers were only introduced after the Romans came into conflict with eastern armies that relied heavily on mounted archery in the 1st century BC. Most notably the Parthians, whose mounted archers were decisive for Crassus's disastrous defeat in the Battle of Carrhae. In the early 1st century CE horse archers were already in widespread use and even supported Roman campaigns against the Germanic tribes in northern Europe.
Document 5: Hoplite: Hoplites were citizen-soldiers of Ancient Greek city-states who were primarily armed with spears and shields. Hoplite soldiers utilized the phalanx formation in order to be effective in war with fewer soldiers. The hoplites were primarily represented by free citizens—propertied farmers and artisans—who were able to afford the bronze armour suit and weapons (estimated at a third to a half of its able-bodied adult male population). Hoplites were not professional soldiers and often lacked sufficient military training. Although some states did maintain a small elite professional unit, hoplite soldiers were relied on heavily and made up the bulk of ancient Greek armies of the time.
Document 6: Polish hussars: The Polish Hussars ( , , or ; Polish: "Husaria" ), or Winged Hussars, were one of the main types of the cavalry in the Polish-Lithuanian Commonwealth between the 16th and 18th centuries. When this cavalry type was first introduced by Serbian and Hungarian mercenary horsemen at the beginning of the 16th century, they served as light cavalry banners in the Polish army; by the second half of the 16th century and after Stephen Báthory's reforms, hussars had been transformed into heavily armored shock cavalry. Until the reforms of the 1770s, the husaria banners were considered the elite of the Polish cavalry.
Document 7: List of Roman gladiator types: There were many different types of gladiators in ancient Rome. Some of the first gladiators had been prisoners-of-war, and so some of the earliest types of gladiators were experienced fighters; Gauls, Samnites, and "Thraeces" (Thracians) used their native weapons and armor. Different gladiator types specialized in specific weapons and fighting techniques. Combatants were usually pitted against opponents with different, but more or less equivalent equipment, for the sake of a fair and balanced contest. Most gladiators only fought others from within the same school or Ludus, but sometimes specific gladiators could be requested to fight one from another Ludus.
Document 8: Military of the Sasanian Empire: The Sasanian army (Middle Persian "Spâh-ī Sāsānīg") was the primary military body of the Sasanian armed forces, serving alongside the Sasanian navy. The birth of the army dates back to the rise of Ardashir I (r. 224–241), the founder of the Sasanian Empire, to the throne. Ardashir aimed at the revival of the Persian Empire, and to further this aim, he reformed the military by forming a standing army which was under his personal command and whose officers were separate from satraps, local princes and nobility. He restored the Achaemenid military organizations, retained the Parthian cavalry model, and employed new types of armour and siege warfare techniques. This was the beginning for a military system which served him and his successors for over 400 years, during which the Sasanian Empire was, along with the Roman Empire and later the East Roman Empire, one of the two superpowers of Late Antiquity in Western Eurasia. The Sasanian army protected "Eranshahr" ("the realm of Iran") from the East against the incursions of central Asiatic nomads like the Hephthalites and Turks, while in the west it was engaged in a recurrent struggle against the Roman Empire.
Document 9: Surena: Surena or Suren or Sourena (died 53 BC) was a Parthian spahbed ("General" or "Commander") during the 1st century BC. He was a member of the House of Suren and was best known for defeating the Romans in the Battle of Carrhae. Under his command Parthians decisively defeated a numerically superior Roman invasion force under the command of Marcus Licinius Crassus. It is commonly seen as one of the earliest and most important battles between the Roman and Parthian empires and one of the most crushing defeats in Roman history.
Document 10: Derafsh Kaviani: Derafsh Kaviani, or Derafsh Kavani, was the legendary royal standard (vexilloid) of Iran used since ancient times until fall of the Sasanian Empire. Following the defeat of the Sassanids at the Arab conquest of Persia, the Sassanid standard was recovered by one Zerar bin Kattab, who received 30,000 dinars for it. After the jewels were removed, Rashidun Caliph Umar is said to have burned the standard. The banner was also sometimes called the "Standard of Jamshid" ("Drafš-ī Jamshid"), the "Standard of Fereydun" ("Drafš-ī Freydun") and the "Royal Standard" ("Drafš-ī Kayi").
Document 11: Svinfylking: The Svinfylking, Old Norse for 'Swine Array' or 'Boar Snout', was a version of the wedge formation used in Iron Age Scandinavia then by the Vikings, and by the Germanic peoples during the Germanic Iron Age where it was known as the "Schweinskopf" or 'Swine's Head'. Its invention was attributed to the god Odin.
Document 12: Lance: The lance is a pole weapon or spear designed to be used by a mounted warrior or cavalry soldier (lancer). During the periods of classical and medieval warfare, it evolved into being the leading weapon in cavalry charges, and was unsuited for throwing or for repeated thrusting, unlike similar weapons of the spear/javelin/pike family typically used by infantry. Lances were often equipped with a vamplate – a small circular plate to prevent the hand sliding up the shaft upon impact. Though best known as a military and sporting weapon carried by European knights, the use of lances was widespread throughout Asia, the Middle East and North Africa wherever suitable mounts were available. As a secondary weapon, lancers of the medieval period also bore swords, axes or maces for hand-to-hand combat, since the lance was often a one-use-per-engagement weapon; assuming the lance survived the initial impact intact, it was (depending on the lance) usually too long, heavy and slow to be effective against opponents in a melee.
Document 13: Light cavalry: Light cavalry, often called Light Horse, comprises lightly armed and lightly armoured troops mounted on horses, as opposed to heavy cavalry, where the riders (and sometimes the horses) are heavily armored. The missions of the light cavalry were primarily reconnaissance, screening, skirmishing, raiding, and most importantly, communications, and were usually armed with spears, swords, bows and later carbines.
Document 14: Byzantine army: The Byzantine army or Eastern Roman army was the primary military body of the Byzantine armed forces, serving alongside the Byzantine navy. A direct continuation of the Roman army, the Eastern Roman army maintained a similar level of discipline, strategic prowess and organization. It was among the most effective armies of western Eurasia for much of the Middle Ages. Over time the cavalry arm became more prominent in the Byzantine army as the legion system disappeared in the early 7th century. Later reforms reflected some Germanic and Asian influences – rival forces frequently became sources of mercenary units e.g.; Huns, Cumans, Alans and (following the Battle of Manzikert) Turks, meeting the Empire's demand for light cavalry mercenaries. Since much of the Byzantine military focused on the strategy and skill of generals utilizing militia troops, heavy infantry were recruited from Frankish and later Varangian mercenaries.
Document 15: Grivpanvar: The Grivpanvar (literally: neck-guard wearer), were an elite late Parthian and Sassanian division who fought as heavy knights or Cataphract cavalry. According to Roman sources, the Grivpanvar had the ability to impale two men on the long, heavy spears that they carried. Historical evidence suggests that the heavily armoured Parthian grivpanvar were at least partially influenced by the military of the Central Asian steppes, who in turn had inherited their armoured cavalry traditions from the Massagetae and the late Achaemenid Persians.
ground_truth: Cataphract