Shloka 6.100.17
रावण–रामयुद्धप्रारम्भः (The Intensification of the Rama–Ravana Duel)
तयोःशरपथंप्राप्यरावणोराजपुत्रयोः ।स बभौ च यथाराहुःसमीपशशिसूर्ययोः ।।6.100.17।।
tayoḥ śarapathaṃ prāpya rāvaṇo rājaputrayoh |
sa babhau ca yathā rāhuḥ samīpa-śaśi-sūryayoḥ ||6.100.17||
When Rāvaṇa came within the arrow-path of the two royal princes, he appeared like Rāhu drawing near the moon and the sun.
That way when the two princes came near the range of Ravana's arrows, it was like the Sun and the moon near planet Rahu.
Adharma is framed as eclipse-like: it approaches to obscure light. Dharma is the sustaining radiance (like sun and moon), while destructive intent is likened to Rāhu.
Rāvaṇa advances close enough to engage Rāma and Lakṣmaṇa directly within effective bow-range.
The princes’ luminous steadfastness (tejas) is implied: they stand as ‘lights’ against the encroaching darkness.