The plot has no bearing on the manga/anime, though it incorporates all the important characters from the story, which feels forced most of the time. Interrupting Yoh Asakura and his friends' well-earned free time from the Shaman King Tournament, a figure who calls himself "Magister" arrives. Proclaiming that he wishes to resurrect the Shaman King from 4,500 years back, he attacks Anna (Yoh's fiancee), causing the book in her hand - The Tome of the Shaman - to be torn apart with its pages scattered. In order to resurrect Mephias, Magister must now retrieve the pages of the book, and in order to stop him, Yoh Asakura must do the same.
Yoh will collect Guardian Ghosts in the maps as well as from enemies and non-player characters, and he can equip five at a time to his Head Phones, Left and Right Glove, and Left and Right Sandal slots, once the four extra ones are found in the game world. The spirits are either Active or Passive, Active ones being activated by pushing the shoulder buttons and Passive ones creating an automatic effect simply by equipping it. Of the five slots, only the Left and Right Gloves allow Yoh to use Active spirits; 'L' and 'R' respectively activate the assigned ghosts. There are four "Decks" of this, allowing the player to - by pressing select while playing the game - switch between different combinations of this. This is a great innovation, though having four Decks makes switching around something the player can't do during combat or in other circumstances that call for a quick change.
There are 68 such ghosts to Aria of Sorrow's 120 souls, the most important ones being: Amidamaru, Yoh's personal spirit who allows him to perform devastating sword combos; Tokageroh, who allows Yoh to push crates; Corey, who freezes fires so they can be destroyed; Eliza, who protects him from poisonous gas; Silva's five spirits which, when equipped all together, allow the prospective Shaman King to blast totem poles that block the way; Mic, who gives him the ability to sprint and jump longer distances; Lee Pai-Long, who lets him slide through tight crevices; Grand Tao Dragon, which lets him skip to the end of a particular map if he's already gone to the end once; Chloe, who lets him latch onto and swing from hooks a la Simon Belmont; Blocks, which literally allows Yoh to create temporary platforms; and Magnescope, which lets the player look around.
Some of the ghosts sap Yoh's SP while others activate automatically. Most of the Guardian Ghosts are mildly amusing but ultimately useless, as was the case in Aria of Sorrow. Moreover, many of them give Yoh abilities he should have automatically. Just as Soma Cruz, in Aria of Sorrow, collects abilities and souls that are automatically apart of his moveset once he collects them, too would abilities like Lee Pai-Long's down-slide, Eliza's protection from poison, and Magnescope's allowing one to look slightly beyond the screen have been better off being automatic or activated as it would be in another platformer. Instead, the player has to pick a small handful of these upgrades to use at once.
Yoh will also collect: 20 Magatama Beads, which increase his maximum health a good deal with every four he obtains; 12 pages to The Tome of the Shaman, which increases his SP one bar every time he gets four; up to 99 Leaf, Pebble, and Doll items, each of which work as ammo to certain Spirit Control abilities; food and other antidote that heal him from damage or poisoning, respectively; and Yen, which he may use to purchase food or antidote while in the overworld map. The Leaves, Pebbles, and Dolls aren't put to much use, while the Magatama Beads and Tome Pages would have been better off as 20 mini-upgrades since having Yoh's bar update in increments makes collecting the first three Magatama Beads in a collection of four much less satisfying.
The game is broken up into several somewhat linear paths connected by dots on an overworld map. There's definitely a non-linearity to the levels and the world as a whole, but until the player picks up the Grand Tao Dragon, the levels must be re-traversed in full in order to get back to that previously out-of-reach spirit or Magatama Bead one remembers seeing earlier. This wouldn't be the worst injustice, but considering the map is quite sprawling, with some journeys from one end to the other surpassing ten paths, this quickly becomes very tedious.
The game as a whole feels like Castlevania, thanks in no small part to its graphics. The world and its enemies have a very Circle of the Moon or Aria of Sorrow-type feel to them, and though this would be unavoidable in any game with such a premise, it does feel more than accidental. The music is great orchestration, standout tracks being the beautifully haunting 'Western Cemetery' and the subdued yet impelling 'Tao Grounds'. There's also: the lively and danceable 'Eastern Cemetery'; the pleasing 'Northern Fields'; the march-like and then sweet 'Southern Mountains'; the soft and happy-go-lucky 'Jungle Ruins'; the ominous, then sweet, then ominous again build up of 'Industrial Area'; the quiet and calming 'Ice Land'; the energetic 'Boss'; and, of course, the triumphant and then eerie 'Main Menu'.
Master of Spirits has a deep spirits system, a sizable world, and a healthy challenge, but tedious backtracking and some problems with the way said spirits system is utilized hold the title back from being as great as its spiritual predecessor.