Srimad Bhagavatam Canto 04, Chapter 24, Text 18

SB 4.24.18

atmaramo ’pi yas tv asya
 loka-kalpasya radhase
saktya yukto vicarati
 ghoraya bhagavan bhavah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Lord Siva, the most powerful demigod, second only to Lord Visnu, is self-sufficient. Although he has nothing to aspire for in the material world, for the benefit of those in the material world he is always busily engaged everywhere and is accompanied by his dangerous energies like the goddess Kali and the goddess Durga.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Lord Siva is known as the greatest devotee of the Supreme Personality of Godhead. He is known as the best of all types of Vaisnavas (vaisnavanam yatha sambhuh). Consequently, Lord Siva has a Vaisnava sampradaya, the disciplic succession known as the Rudra sampradaya. Just as there is a Brahma sampradaya coming directly from Lord Brahma, the Rudra sampradaya comes directly from Lord Siva. Lord Siva is one of the twelve great personalities, as stated in Srimad-Bhagavatam (6.3.20):
svayambhur naradah sambhuh
 kumarah kapilo manuh
prahlado janako bhismo
 balir vaiyasakir vayam
These are twelve great authorities in preaching God consciousness. The name Sambhu means Lord Siva. His disciplic succession is also known as the Visnusvami sampradaya, and the current Visnusvami sampradaya is also known as the Vallabha sampradaya. The current Brahma sampradaya is known as the Madhva-Gaudiya sampradaya. Even though Lord Siva appeared to preach Mayavada philosophy, at the end of his pastimes in the form of Sankaracarya he preached the Vaisnava philosophy: bhaja govindam bhaja govindam bhaja govindam mudha-mate. He stressed worshiping Lord Krsna, or Govinda, three times in this verse and especially warned his followers that they could not possibly achieve deliverance, or mukti, simply by word jugglery and grammatical puzzles. If one is actually serious to attain mukti, he must worship Lord Krsna. That is Sripada Sankaracarya’s last instruction.
Herein it is mentioned that Lord Siva is always accompanied by his material energy (saktya ghoraya). Material energy — goddess Durga, or goddess Kali — is always under his control. Goddess Kali and Durga serve him by killing all the asuras, or demons. Sometimes Kali becomes so infuriated that she indiscriminately kills all kinds of asuras. There is a popular picture of goddess Kali in which she wears a garland composed of the heads of the asuras and holds in her left hand a captured head and in her right hand a great khadga, or chopper, for killing asuras. Great wars are symbolic representations of Kali’s devastation of the asuras and are actually conducted by the goddess Kali:
srsti-sthiti-pralaya-sadhana-saktir eka
(Brahma-samhita 5.44)
Asuras try to pacify the goddess Kali, or Durga, by worshiping her in material opulence, but when the asuras become too intolerable, the goddess Kali does not discriminate in killing them wholesale. Asuras do not know the secret of the energy of Lord Siva, and they prefer to worship the goddess Kali or Durga or Lord Siva for material benefit. Due to their demoniac character, they are reluctant to surrender to Lord Krsna, as indicated by Bhagavad-gita (7.15):
na mam duskrtino mudhah
 prapadyante naradhamah
 asuram bhavam asritah
Lord Siva’s duty is very dangerous because he has to employ the energy of the goddess Kali, or Durga. In another popular picture the goddess Kali is sometimes seen standing on the prostrate body of Lord Siva, which indicates that sometimes Lord Siva has to fall down flat in order to stop the goddess Kali from killing the asuras. Since Lord Siva controls the great material energy (the goddess Durga), worshipers of Lord Siva attain very opulent positions within this material world. Under Lord Siva’s direction, a worshiper of Lord Siva gets all kinds of material facilities. In contrast, a Vaisnava, or worshiper of Lord Visnu, gradually becomes poorer in material possessions because Lord Visnu does not trick His devotees into becoming materially entangled by possessions. Lord Visnu gives His devotees intelligence from within, as stated in Bhagavad-gita (10.10):
tesam satata-yuktanam
 bhajatam priti-purvakam
dadami buddhi-yogam tam
 yena mam upayanti te
“To those who are constantly devoted and worship Me with love, I give the understanding by which they can come to Me.”
Thus Lord Visnu gives intelligence to His devotee so that the devotee can make progress on the path back home, back to Godhead. Since a devotee has nothing to do with any kind of material possession, he does not come under the control of the goddess Kali, or the goddess Durga.
Lord Siva is also in charge of the tamo-guna, or the mode of ignorance in this material world. His potency, the goddess Durga, is described as keeping all living entities in the darkness of ignorance (ya devi sarva-bhutesu nidra-rupam samsthita). Both Lord Brahma and Lord Siva are incarnations of Lord Visnu, but Lord Brahma is in charge of the creation whereas Lord Siva is in charge of the destruction, which he carries out with the help of his material energy, goddess Kali, or goddess Durga. Thus in this verse Lord Siva is described as being accompanied by dangerous potencies (saktya ghoraya), and that is the actual position of Lord Siva.
Srimad Bhagavatam Canto 04, Chapter 24, Text 17
Srimad Bhagavatam Canto 04, Chapter 24, Text 19