Canto 3 -
Araṇya-kāṇḍa
Chapter 31: Rāvaṇa’s Conversation with Akampana and Mārīca
Text 3.31.2

जनस्थानस्थिता राजन्राक्षसा बहवो हताः।
खरश्च निहतः सङ्ख्ये कथञ्चिदहमागतः॥

janasthāna-sthitā rājan rākṣasā bahavo hatāḥ
kharaś ca nihataḥ saṅkhye kathañcid aham āgataḥ

janasthāna-sthitāḥ = in Janasthāna; rājan = O king; rākṣasāḥ = rākṣasas; bahavaḥ = many; hatāḥ = have been killed; kharaḥ = Khara; ca = also; nihataḥ = has been killed; saṅkhye = in battle; kathañcit = somehow; aham = I; āgataḥ = have come [here].

O king, many rākṣasas in Janasthāna have been killed! Khara has also been killed in battle! I have somehow come [here].

“Somehow” implies that [Akampana] had assumed the form of a woman.

Therefore Śūrpaṇakhā will state:

ekā kathañcin muktāhaṁ paribhūya mahātmanā
strī-vadhaṁ śaṅkamānena rāmeṇa viditātmanā

“Somehow I was released by the greatly powerful Rāma after being subdued [by Him, for] that renowned soul was apprehensive that a woman would be killed.”1 (Rāmāyaṇa 3.34.11)

1 Rāma spared Śūrpaṇakhā because she was a woman. Similarly, Akampana was spared by Him because he had assumed the form of a woman. This is an apt and reasonable answer to the question, “How come Akampana got out of the fray?”