So far, all I've found (in the Prose) is the line "The champions of Hel follow Loki, and the Sons of Muspell shall have a company by themselves, and it shall be bright." from when the Jotunkin assemble themselves upon the field of Vigridr.
From what I can read in the Voluspo, Ragnarok is total war - everybody fights, even in Midgard, the mortal world. It says in Voluspo. 45:
Brothers shall fight and fell each other,
And sisters' sons shall kinship stain;
Hard is it on earth, with mighty whoredom;
Axe-time, sword-time, shields are sundered,
Wind-time, wolf-time, ere the world falls;
Nor ever shall men each other spare.
In Voluspo 46, the seas grow rough and Hel-roads open
Fast move the sons of Mim (water spirits), and fate
Is heard in the note of the Gjallarhorn;
Loud blows Heimdall, the horn is aloft,
In fear quake all who on Hel-roads are.
Apparently, all the dead are conscripted into Hela's army. Of course unwilling soldiers aren't too good.
In Voluspo 48 it shows that the other races of the Nine Worlds also are locked in battle:
How fare the gods? how fare the elves?
All Jotunheim groans, the gods are at council;
Loud roar the dwarfs by the doors of stone,
The masters of the rocks: would you know yet more?
In Voluspo 50, Hrym leads the frost-giants, the Midgard Serpent rises from the sea and Naglfar is launched.
From the east comes Hrym with shield held high;
In giant-wrath does the serpent writhe;
O'er the waves he twists, and the tawny eagle
Gnaws corpses screaming; Naglfar is loose.
Naglfar means nail-ship. It has been under construction since the beginning of the age. It is made of the fingernails of dead. For this reason when someone is buried you are supposed to cut their fingernails, so they don't add too much to the building of Naglfar.
In Voluspo 51 the Fenris and his kin join in, and Loki assumes the captaincy of Naglfar to claim his final title as Captain of the Dead. It is the only title remaining to him.
O'er the sea from the north there sails a ship
With the people of Hel, at the helm stands Loki;
After the wolf do wild men follow,
And with them the brother of Byleist (Loki) goes.
And finally Surt the Firelord and the Fire-wights joins the battle in Voluspo 52
Surt fares from the south with the scourge of branches (fire-wights),
The sun of the battle-gods shone from his sword;
The crags are sundered, the giant-women sink,
The dead throng Hel-way, and heaven is cloven.
Pretty intense stuff...
Runesinger