How to Get All the Spells and Miracles in Demon's Souls

Getting the platinum trophy in Demon's Souls is not an easy task, and it requires several playthroughs. You need to rescue certain NPCs that sell the spells. Acquiring all the spells and miracles will unlock two trophies - Sage's Trophy [All Magic Spells Obtained] and Saint's Trophy [All Miracles Obtained].

Certain spells and miracles require the same boss soul to be exchanged for them, so copies of the same boss soul are required. Thus, additional playthroughs are mandatory for these trophies. However, this means that anything you might have missed in one playthrough, you can acquire in a subsequent playthrough as all the spells and miracles carry over.

First, you need to do some re-requisite tasks.

Pre-Requisites

NPCs that sell Spells and Miracles

Saint Urbain – In the second area of the Shrine of Storms, you will need to head to the bottom of the area where you encounter the first Grim Reaper looking enemy, and then you need to head behind the staircase. Patches will be there, waiting to kick you down into a pit with Saint Urbain, who needs to be rescued. Saint Urbain teaches all the Miracles present in the game. Completing this rescue also unlocks the trophy Umbasa [Rescue Saint Urbain].
Sage Freke the Visionary – Sage Freke the visionary is in one of the cells inside the Prison of Hope. You need to acquire the Special Key, which is located just before the Fool’s Idol on the wall behind the praying enemy. You have to kill the enemy to make the Idol vulnerable. Then, you need to head back to Sage Freke's cell and open it in order to rescue him. He teleports to the Nexus. Completing this rescue also unlocks the trophy A Dash Of Sage [Rescue Sage Freke the Visionary].
Yuria the Witch – For this, you need to unlock the third area of the Boletarian Palace. Once unlocked, head through the area and kill the Fat Officials. You can recognise them with their portly demeanor and weird laugh. Once you acquire the items they drop - Iron Ring of Keys and Official’s Cap, head back to the area just before the boss arena where you fought the Tower Knight, and open a door there using the Iron Ring of Keys. Inside, you can find Biorr, who can be rescued from a cell. There will also be another Fat Official here that will drop the Bloody Key. With all that done, head over to Stonefang Mines and start farming the Fat Officials there. This is in order to acquire the remaining parts of the Official Set. Once you have the whole set, with the key, head back to the area before the boss arena where you fought the Tower Knight again, and open the gate. Head down the path into a tower with a fat official right above you. Equip the set you just farmed and he will lower the stairs for you. Defeat the Fat Official there, unequip the Official Set, and talk to Yuria. This rescues her and allows her to teleport to the Nexus. She is needed in order to learn all the Spells. Completing this rescue also unlocks the trophy Witch in the Tower [Rescue Yuria the Witch].

Boss Souls required to learn the spells and Miracles

Storm Demon’s Soul [This unlocks Storm King's Trophy (Slayer of the demon "Storm King")] – You need ONE copy of this soul.
Yellow Demon’s Soul [This unlocks Old Monk's Trophy (Slayer of the demon "Old Monk")] – You need THREE copies of this soul.
Wriggling Demon’s Soul [This unlocks Leechmonger's Trophy (Slayer of the demon "Leechmonger")] – You need TWO copies of this soul.
Dragon Demon’s Soul [This unlocks Dragon God's Trophy (Slayer of the demon "Dragon God")] – You need THREE copies of this soul.
Swollen Demon’s Soul [This unlocks Adjudicator's Trophy (Slayer of the demon "Adjudicator")] – You need ONE copy of this soul.
Pureblood Demon’s Soul [This unlocks Maiden Astrea's Trophy (Slayer of the demon "Maiden Astrea")] – You need THREE copies of this soul.
Hero Demon’s Soul [This unlocks Old Hero's Trophy (Slayer of the demon "Old Hero")] – You need ONE copy of this soul.
Eroded Demon’s Soul [This unlocks Dirty Colossus' Trophy (Slayer of the demon "Dirty Colossus")] – You need ONE copy of this soul.
Hard Demon’s Soul [This unlocks Armor Spider's Trophy (Slayer of the demon "Armor Spider")] – You need TWO copies of this soul.
Silver Demon’s Soul [This unlocks Penetrator's Trophy (Slayer of the demon "Penetrator")] – You need TWO copies of this soul.
Doll Demon’s Soul [This unlocks Fool's Idol's Trophy (Slayer of the demon "Fool's Idol")] – You need ONE copy of this soul.
Iron Demon’s Soul [This unlocks Tower Knight's Trophy (Slayer of the demon "Tower Knight")] – You need ONE copy of this soul.

Colorless Demon's Souls (dropped by Primeval Demons)

A total of three Colorless Demon’s Souls are required, which are only dropped by Primeval Demons who only spawn in Pure Black World Tendency. Here's a guide on how to change World Tendency, and how it affects the game. One spawns in a specific location in each Archstone.

In the Boletarian Palace, where you find the Official’s Cap in the third area, go up the set of stairs on the right-hand side to find the Primeval Demon.
In the Stonefang Mines, go to the first area and into the place underneath the falling boulders. Rotate the crank and take the lift from the balcony all the way down to find it the Primeval Demon.
In the Tower of Latria, a huge human centipede enemy guards the Primeval Demon in the swamp in the second area.
In the Shrine of Storm, drop down to the left of where the first Grim Reaper is in the second area. There will be a passage to the left. Go down there and find an illusory wall. Go through it and face the skeleton enemy with the Dual Katanas. Kill it and keep going down the path to find it the Primeval Demon.
In the Valley of Defilement, the Primeval Demon is in the swamp in the second area near the slug nest.

Learning All Spells and Miracles

All the Miracles

Some miracles can be bought from any miracle teacher. These are as follows -

Antidote - This miracle can be learned for 3,000 Souls
Evacuation - This miracle can be learned for 20,000 Souls
Heal - This miracle can be learned for 5,000 Souls
Hidden Soul - This miracle can be learned for 3,000 Souls

Some miracles can only be bought from Saint Urbain. These are as follows -

Anti-Magic Field - This miracle can be learned by exchanging for the Storm Demon’s Soul [Storm King]
Banish - This miracle can be learned by exchanging for the Yellow Demon’s Soul [Old Monk]
Cure - This miracle can be learned by exchanging for the Wriggling Demon’s Soul [Leechmonger]
God’s Wrath - This miracle can be learned by exchanging for the Dragon Demon’s Soul [Dragon God]
Recovery - This miracle can be learned by exchanging for three Colorless Demon’s Souls [Primeval Demons]
Regeneration - This miracle can be learned by exchanging for the Swollen Demon’s Soul [Adjudicator]
Resurrection - This miracle can be learned by exchanging for the Pureblood Demon’s Soul [Maiden Astraea]
Second Chance - This miracle can be learned by exchanging for the Hero Demon’s Soul [Old Hero]

All the Spells

Some spells can be learned from any spell teacher. These are as follows.

Cloak - This spell can be learned for 500 Souls
Demon’s Prank - This spell can be learned for 500 Souls
Flame Toss - This spell can be learned for 1,000 Souls
Enchant Weapon - This spell can be learned for 5,000 Souls
Protection - This spell can be learned for 5,000 Souls
Soul Arrow - This spell can be learned for 1,000 Souls
Water Veil - This spell can be learned for 500 Souls

Some spells can be learned only from Sage Freke. These are as follows.

Acid Cloud - This spell can be learned by exchanging for the Eroded Demon’s Soul [Dirty Colossus]
Death Cloud - This spell can be learned by exchanging for the Pureblood Demon’s Soul [Maiden Astraea]
Fireball - This spell can be learned by exchanging for the Dragon Demon’s Soul [Dragon God]
Fire Spray - This spell can be learned by exchanging for the Hard Demon’s Soul [Armor Spider]
Homing Soul Arrow - This spell can be learned by exchanging for the Yellow Demon’s Soul [Old Monk]
Light Weapon - This spell can be learned by exchanging for the Silver Demon’s Soul [Penetrator]
Poison Cloud - This spell can be learned by exchanging for the Wriggling Demon’s Soul [Leechmonger]
Soul Ray - This spell can be learned by exchanging for the Doll Demon’s Soul [Fool’s Idol]
Warding - This spell can be learned by exchanging for the Iron Demon’s Soul [Tower Knight]

Some spells can be learned only from Yuria the Witch. These are as follows.

Cursed Weapon - This spell can be learned by exchanging for the Silver Demon’s Soul [Penetrator]
Firestorm - This spell can be learned by exchanging for the Dragon Demon’s Soul [Dragon God]
Ignite - This spell can be learned by exchanging for the Hard Demon’s Soul [Armor Spider]
Relief - This spell can be learned by exchanging for the Pureblood Demon’s Soul [Maiden Astraea]
Soulsucker - This spell can be learned by exchanging for the Maiden In Black Demon’s Soul [IMPORTANT: Don’t kill Maiden in Black at the end of the game. If you kill her you will not get the soul]
Soul Thirst - This spell can be learned by exchanging for the Yellow Demon’s Soul [Old Monk]