Blood Sword

Blood Sword is a series of gamebooks created by Oliver Johnson and Dave Morris and published by Knight Books in the late 1980s. It was set in the invented fantasy world of "Legend", the authors' own fantasy world, which was the setting for their Dragon Warriors role playing game too. The storyline involved a group of adventurers who, after emerging victorious from a grueling adventure in the Battlepits of Krarth, stumbled by pure chance upon the plot of the five True Magi, evil entities who were thought to have been destroyed during a catastrophic magic explosion centuries before, and are now trying to reincarnate on Earth and bring about eternal damnation. After surviving an attack from a couple of henchmen of Blue Moon (the eldest and most powerful of the Magi), the adventurers are given the scabbard of Blood Sword, the only weapon the True Magi actually fear, by an old man mortally wounded in the attack... and from thereon, begin their quest to reunite the pieces of the sacred sword and stop the True Magi before the end of the Millennium and the coming of Judgement Day.

The books are designed for multi-player, co-operative play, though there was also a single-player option, and one player could control more than one character at a time. A party could consist of up to four players, with each player being either a Sage, Enchanter, Trickster or Warrior. Each of the classes was well-balanced and offered a different playing style from the others. Characters advanced in level, gaining power as the series progressed, and were carried forward from book to book, giving the experience of one long story.

Each player was autonomous - often paragraphs would be for one player's eyes only, and he would be privy to some information that he was free to withhold from the rest of his party.

The first three books were also adapted into a children's book series (also three books) called The Chronicles of the Magi in the late 1990s by Dave Morris. They featured several of the events and plot points used in the Blood Sword series, although with some change in the order they happen in. Two original characters, Altor and Caelestis (a warrior-monk and a thief), take what would be the player's role in the story.

Tropes used in Blood Sword include:

Action Girl: Possibly. The gender of the adventurers is unspecified, so you can imagine some or all of them to be female.
Anti-Hero: The adventurers are all Type 2, though the Trickster can lapse into Type 3 or even 4 at times.
Attack Backfire: In one of the gamebooks you could try dealing with a huge Djinni by blasting it with the Orb of Fire. He finds it refreshing and it doesn't end well for the character attempting it...
Badass Normal: The Warrior and the Trickster.
Big Bad: The True Magi, though Blue Moon is the most prominent.
Charm Person: The Servile Enthrallment spell. Not surprisingly, it's the hardest spell to cast.
Combat Medic: The Sage
Eldritch Abomination: The True Magi were humans once, but now they have become this. It was actually their plan all along.
The End of the World as We Know It: The end of the Millennium is coming. Somewhat played with in that you are not out to prevent it, but rather to make sure the True Magi cannot infest the world with their evil, so that when God comes to judge humanity, He will find it worthy of Heaven.
Evil Prince: Susurrien
Fire and Brimstone Hell: Red Death's personal domain.
Forgot About His Powers: There are times when the Enchanter apparently forgets s/he has a teleporting spell.
Guile Hero: The Trickster
Infinity+1 Sword: The Blood Sword, the sword created by the Archangels to destroy the living dead.
Jerkass: You will hate the Faltyns. Trust me, you will.
Master of Illusion: Blue Moon
My Name Is Not Icon: It's actually Aiken of the Song Mountain. You foreign devils, always getting his name wrong...
Nintendo Hard: These gamebooks are hard. They become really hard when you don't have a Sage.
Our Giants Are Bigger: There's at least one opponent of this type in every book: Skrymir in Book 1, Thanatos in 2, the female cyclops in 3, Typhon and Garm in 4, Snorrid in 5.
Plaguemaster: Plague Star. Also Nasu, on a smaller scale...
Recurring Boss: Icon will make your life hell in both Books 1 and 3. And even Book 4, while he's at it.
Revenge Before Reason: Icon lives and breathes this trope...
Shock and Awe: The Enchanter's most powerful spells, Sheet Lightning and Nemesis Bolt, are all electricity-based
Squishy Wizard: The Enchanter
Thanatos Gambit: One of the possible endings of the series. Remember, the final judgement is minutes away so if the last of the True Magi currently exists only as an illusion in your mind, dying before he can become physical can win you the game.
The Undead: Blood Sword is particularly effective against them... and the True Magi are among their number!
Worthy Opponent: {{[spoiler|Icon seems to consider you this after you defeat him for the final time in Book 4.}}