List of Ravan's allies.

Doosan's other brother's:

"The two younger brothers of Dushana, Vajravega and Promathin, will join thee with their forces!' And having said this unto the mighty Kumbhakarna. the Rakshasa king gave instructions to Vajravega and Promathin as to what they should do. And accepting his advice, those two warlike brothers of Dushana quickly marched out of the city, preceded by Kumbhakarna."

https://www.sacred-texts.com/hin/m03/m03284.htm

Avindhya;

"old and wise counsellor (of Ravana) known by the name of Avindhya"

https://www.sacred-texts.com/hin/m03/m03289.htm

Ravan was not a king he was actually a Emperor:

"Placed as thou art on the blazing throne of an empire, it behoveth thee not to slay a woman!"

https://www.sacred-texts.com/hin/m03/m03287.htm

Logic; this would mean that Ravan could have called on other king's who were dependent on him for support. If he called or sent a message they would fight Ram and Vanaras for him.

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Vibeeshan mentioned them right before Meghanad was deceived.

[Quote]

"Prahasta was killed. The valiant Nikumbha, the mighty Kumbhakarna, Kumbha, the demon called Dhumraksha, Jambumali, Mahamali, the highly swift Ashaniprabha, Suptaghna, Yajnakopa, a demon named Vajradamshtra, Samhadri, Vikata the destroyer of enemies, Tapana, Manda, Praghaasa, Praghasa, PrajaNgha, JaNga, Agniketu who was difficult to be conquered, Agniketu, the valiant Rashmiketu, vidyujjihva, Dvijihva, Suryashatru, Akampana, Suparshva, Chakramali, Kampana and the mighty Devantaka & Narantak were also killed."

[End]

https://www.valmikiramayan.net/utf8/yuddha/sarga89/yuddha_89_frame.htm

31 warriors got mentioned (excluding the second Agniketu).

But the death's of Tapana & a couple here were not shown in any previous Sarga.

=

2 other's are mentioned (ignoring Dvijihva, Kumvakarna & Mahodar)

"Announce (by a beat of drum in the city-streets) that myself, Dvijihva, Samhraadi, Kumbhakarna and Vitardana these five demons are setting out for the battle to kill Rama."

https://www.valmikiramayan.net/utf8/yuddha/sarga64/yuddha_64_frame.htm

Identities - "Samhraadi" & "Vitardana".

Logic: Samhraadi is not Samhadri, notice how the R is placed differently they are two different people.

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A rakshasa literally named Atirath:

"For that which, because of arrogance, neither Atiratha nor Narantaka nor you yourself has agreed to my counsel, the consequence of it has come now."

http://valmikiramayan.pcriot.com/utf8/yuddha/sarga109/yuddha_109_frame.htm

Logic - vibeeshan gave counsel to Ravan & Atirath.

All were stronger than the foot soldier's who defeated Hanuman & Karna.