Meaning of the sloka
Then all the rakshasas who were living in Rasatala, took refuge in Ravana and lived happily in Lanka.
Here Ravana is referred to as Dashanana.
Daśānana is a Sanskrit compound consisting of the terms daśan and ānana (आनन). The meaning of the same is ‘One with ten heads’.
Moral here is that in the presence of a leader, even the weaker sect could become braver and follow the leader.The mere presence of a power like that could awaken the spirit of the followers.
In the Puranas and in the Atharvaveda, there are 14 worlds, seven higher ones (Vyahrtis) and seven lower ones (Pātālas), viz. bhu, bhuvas, svar, mahas, janas, tapas, and satya above and atala, vitala, sutala, rasātala, talātala, mahātala, pātāla.
The seven higher ones are mentioned in the Pranayama which is said during the Sandhyavandhanam, a ritual conducted daily by brahmins. The Pranayama mantra goes like this.
Om Bhuuh Om Bhuvah Om Svah
Om Mahah Om Janah Om Tapah Om Satyam
Om Tat-Savitur-Varennyam Bhargo Devasya Dhiimahi
Dhiyo Yo Nah Pracodayaat |
Om Aapo Jyotii Raso[a-A]mrtam Brahma Bhuur-Bhuvah Svar-Om
Om, (I meditate on the) Bhu Loka (Physical Plane, Consciousness of the Physical Plane),
Om, (I meditate on the) Bhuvar Loka (Antariksha or Intermediate Space, Consciousness of the Prana),
Om, (I meditate on the) Swar Loka (Swarga, Heaven, Consciousness of the beginning of the Divine Mind),
(The above have relatively grosser manifestations to start the meditation; Then the meditation goes to subtler levels)
Om, (I meditate on the) Mahar Loka (Great, Mighty, Still subtler Plane felt as All-Pervading Consciousness),
Om, (I meditate on the) Janar Loka (Generating, Still subtler Plane felt as All-Creating Consciousness),
Om, (I meditate on the) Tapo Loka (Filled with Tejas, Still subtler Plane felt as filled with Divine Tejas or Illumination of Shakti),
Om, (I meditate on the) Satya Loka (Absolute Truth, Most subtle Plane merging with the Consciousness of Brahman),
Om, on that Savitur (Divine Illumination) which is most Adorable (Varenyam) and which is of the nature of Divine Effulgence (Bhargo Devasya), I meditate,
May that Divine Intelligence (Dhiyah) Awaken (Pracodyat) our (Spiritual Consciousness)
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My primary source for meanings of the slokas is from the E-book published by http://hinduebooks.blogspot.com.
Om Namo Narayanaya