योगवासिष्ठः yogavāsiṣṭhaḥ - book-1, chapter-33, verse-13

अथास्यां सिद्धसेनायां पतन्त्यां नभसो रसाम् ।
उत्तस्थौ मुनिसंपूर्णा तदा दाशरथी सभा ॥ १३ ॥

athāsyāṃ siddhasenāyāṃ patantyāṃ nabhaso rasām ,
uttasthau munisaṃpūrṇā tadā dāśarathī sabhā 13

13. atha asyām siddhasenāyām patantyām nabhasaḥ
rasām uttasthau munisaṃpūrṇā tadā dāśarathī sabhā

13. atha asyām siddhasenāyām nabhasaḥ rasām patantyām satyām,
tadā munisaṃpūrṇā dāśarathī sabhā uttasthau

13. Then, as this army of perfected beings (siddhas) descended from the sky towards Rasā (the netherworld), the assembly of Daśaratha, filled with sages, rose up.

Words meanings summery:

• अथ (atha) - then, now, thereupon, consequently

• अस्याम् (asyām) - in this (feminine)

• सिद्धसेनायाम् (siddhasenāyām) - in the army of perfected beings (siddhas)

• पतन्त्याम् (patantyām) - while falling, descending, moving downwards

• नभसः (nabhasaḥ) - from the sky, of the sky

• रसाम् (rasām) - towards Rasā, referring to the netherworld or a mythical subterranean stream/region (to Rasā (a mythical netherworld river/region), to the earth)

• उत्तस्थौ (uttasthau) - rose up, stood up, emerged

• मुनिसंपूर्णा (munisaṁpūrṇā) - filled with sages, complete with ascetics

• तदा (tadā) - then, at that time

• दाशरथी (dāśarathī) - pertaining to Daśaratha, indicating his royal assembly (belonging to Daśaratha, related to Daśaratha)

• सभा (sabhā) - assembly, court, council, gathering

Words meanings and morphology

अथ (atha) - then, now, thereupon, consequently

(indeclinable)

अस्याम् (asyām) - in this (feminine)

(pronoun)

Locative, feminine, singular of idam

idam - this, this one

सिद्धसेनायाम् (siddhasenāyām) - in the army of perfected beings (siddhas)

(noun)

Locative, feminine, singular of siddhasenā

siddhasenā - army of Siddhas, host of perfected beings

Compound type : tatpuruṣa (siddha+senā)

• siddha – perfected, accomplished, adept, a perfected being
  noun (masculine)
  Past Passive Participle
  Derived from the root 'sidh' (to accomplish, succeed).
  Root: sidh (class 1)
• senā – army, host, troop
  noun (feminine)

पतन्त्याम् (patantyām) - while falling, descending, moving downwards

(adjective)

Locative, feminine, singular of patat

patat - falling, descending

Present Active Participle

Present active participle of the root 'pat' (to fall).

Root: pat (class 1)

Note: Agrees with 'siddhasenāyām'.

नभसः (nabhasaḥ) - from the sky, of the sky

(noun)

Ablative, neuter, singular of nabhas

nabhas - sky, atmosphere, heaven

रसाम् (rasām) - towards Rasā, referring to the netherworld or a mythical subterranean stream/region (to Rasā (a mythical netherworld river/region), to the earth)

(noun)

Accusative, feminine, singular of rasā

rasā - earth, mythical river/region, netherworld, underground

उत्तस्थौ (uttasthau) - rose up, stood up, emerged

(verb)

3rd person , singular, active, perfect (liṭ) of utthā

Prefix: ut

Root: sthā (class 1)

मुनिसंपूर्णा (munisaṁpūrṇā) - filled with sages, complete with ascetics

(adjective)

Nominative, feminine, singular of munisaṃpūrṇa

munisaṁpūrṇa - filled with sages

Compound type : tṛtīyā tatpuruṣa (muni+saṃpūrṇa)

• muni – sage, ascetic, silent one
  noun (masculine)
• saṃpūrṇa – full, complete, filled
  adjective (masculine)
  Past Passive Participle
  Past passive participle of root 'pṛ' (to fill) with prefix 'sam'.
  Prefix: sam
  Root: pṛ (class 9)

Note: Agrees with 'sabhā'.

तदा (tadā) - then, at that time

(indeclinable)

दाशरथी (dāśarathī) - pertaining to Daśaratha, indicating his royal assembly (belonging to Daśaratha, related to Daśaratha)

(adjective)

Nominative, feminine, singular of dāśarathī

dāśarathī - related to Daśaratha, belonging to Daśaratha

Derived from Daśaratha with suffix -i.

Note: Agrees with 'sabhā'.

सभा (sabhā) - assembly, court, council, gathering

(noun)

Nominative, feminine, singular of sabhā

sabhā - assembly, court, council, meeting hall