We find a nice description about Shani-Deva in our puranas like Skanda Purana & Padma purana.
Puranas tells us that Shani Deva is sun's son. He gained favour of Lord Mahadeva. And Lord Mahadeva granted him the status of planet. He is also called in puranas as "Sauri" or "Surishwara".
He is said to be a downward-look.Gods ,Asuras & humans are get affected by his look & fear him.So he is a fierce deity.
There is a story of King Dasharatha & Shani Deva. King Dasharatha composed a hymn to Shani-Deva , and Shani Deva became pleased with him.
How to please Shani-Deva
Padma purana Part 2 , chapter 52 , in the chapter "The worship of the planets"
20-21a : For the worship of Shanaischara (i.e. Saturn ) one should draw
a circle (i.e. figure) resembling a human figure with black powders
and there should devoutly worship the planet with black sandle , black
flowers , pieces of cloth of that kind (black).
21b-22 : Iron and other gifts should be given also oil cakes &
sesamums. The present for shani being unfavorable is black cow and a
black garment.One should also give according to one's capacity gold
23 : One should recite the hymn - O sun's son , O glorious one ,O you
very mighty one , O you having downward look , O shani be pleased by
means of these presents made by me.
24 : He who having thus devoutly pleased shani ,would give presents to
Brahmanas has shani favourable to him.If he was unfavourable at his
birth and passing to other zodiacal sign.
This is what Skanda-Purana says -:
Skanda Purana ,Book 7 - PRABHASA KANDA , Chapter 49 , "Sanaicaresvara"
4 : The lord without beginning or death was bought down to the linga by
him.Due to his devotion to shambhu he gained his favour & status of
5-7 : The great community of devas and asuras is afraid of his adverse
look.In whole of the cosmos consisting of mobile & immobile beings
,there is no living being ,Deva or Danava who is not affected by sauri
The devotee should worship saureshwara shiva with devoutly on
saturdays with sami leaves and rice cooked with gingerly seeds , black
gram and jaggery.After offering libations according to injections ,he
should offer a black bull to Brahmanas.
It was Shani who was said to have burnt off head of
नीलांजन समाभासम रवि पुत्रम यमाग्रजं ।
छाया मार्तान्ड समभुतम तं
नमामि शनैश्चरम ।।
NILANJANA SAMABHASAM RAVI PUTRAM YAMAGRAJAM | CHAYA MARTHANDA
SAMBHUTAM TAM NAMAMI SHANAISCHARAM ||
Meaning- Oh god dressed in blue silk, who has a blue body, Who wears a
crown, who sits on vulture, Who gives misfortunes, who is armed with a
bow, Who has four hands and who is son of Sun God, Be pleased with me
always and happily grant me boons.