Sacrifice's single player campaign consists of sets of 5 missions, one for each of five gods that the wizard can choose to work for. In addition to having different missions, each god also grants its own set of creatures for summoning and spells to be cast to the wizard. Not only does the player receive different spells from each god, but depending on which gods he chooses to support, the story changes drastically, creating several different endings. It is notable that once you serve a god, some other gods who see him/her as a rival may not provide you any chance to serve him later, hence limiting the gods you can choose and avoid a "triumph combination" of creatures and spells. As an incentive to completing various hidden objectives or simply performing brilliantly in-game, one of the five Gods can appear during or at the end of a mission, granting the player a special boon, the likes of which vary greatly. For instance, Stratos regularly grants players a boon of bonus mana points or speed. Other gods, like James can grant the player an increase in defense, or attack, in healing ability etc.
Sacrifice also possesses a bonus feature once the player has completed the game. The Player is allowed to choose their own character as a side rather than a God in multiplayer. The effect: The player's wizard develops according to the story line, keeping the benefits of boons and mixed creatures and spells, giving some players, an edge over regular players.
The resources (a common element in RTS games) in Sacrifice are souls and mana.
Mana is used for casting any spell, summoning creatures, and is an unlimited, slowly generating resource. A manafountain is a neutral structure existing on the map and cannot be created throughout the game, but provides mana for any players nearby. To claim a neutral manafountain to be your own one, you can summon a Manalith on it, so it will provide mana only for you and your friendly creatures. Manahoars, a summoned creature, can draw energy from your manaliths and give you mana even when you are at a distance from your manaliths.
Souls are used for summoning creatures, and are limited; no new souls can be created during the game. Souls cannot be destroyed unless a unit falls off the map, in which case the soul or souls contained in that creature is forever destroyed. Several creature abilities, such as Consume Soul and Rend Soul, also destroy the soul but are accompanied by other special effects.
Souls exist on the map in two forms: blue souls and red souls. Blue souls are either neutral souls that are placed on the map by the map makers waiting to be picked up by any wizard or souls that are released from the corpse of friendly creatures. These blue souls can be picked up directly by the wizard when he walks near them. Red souls are hostile souls that are released from the corpses of hostile creatures. Red souls cannot be picked up directly, and the wizard has to cast a spell Convert to summon a Sac doctor that will carry the corpse to its summoner's altar and carry out a ritual to purify the souls. During the transportation, the Sac doctor could be killed and the corpse released back to its former master.
The sole aim of this game to win, is to desecrate the enemy's altar. To do this, you have to approach your enemy's altar and cast a spell "Desecrate" with one of your creatures as a sacrifice. A group of Sac doctors will be summoned and perform a ritual to desecrate the altar. During the process, the enemy wizard will suffer damage sent from the ethereal realm. The stronger the creature you have sacrificed, the more the damage is. If he is killed during the process, the desecration is done. If any of the Sac doctors are killed, the desecration will be interrupted and your sacrifice offering will be released free.
A god's power can reveal itself in any part of the world except other god's capitals, in which the Ultimate Altar of that god was set up to collect the faith of the god's people, which is the primary necessity of every god. Gods also establish a connection between themselves and their wizards through a wizard's altar. Thus wizards are the manifestation of gods to accomplish the god's will. Wizards can never be truly killed if the connection exists, and the god can resurrect the wizard somewhere else. But if a wizard is killed and he has no altar (or no connection with their god) at the time of death, they are dead forever and cannot come back.
In his now-destroyed homeworld of Jhera, Eldred was a man of substance (a lord or a king, he doesn't specify, though he was most certainly a tyrant, though in the end of the Pyro missions, it is hinted he was a emperor ) and one of many who vied for power. He spent his life forging another man's empire, but when the young monarch died at far too young an age, power and dominion fell to Eldred alone. Despised by his subjects, foreign powers and internal conspirators sought to tear his kingdom apart. Having dabbled in alchemy and conjuration before, Eldred was forced to turn his hobby into a serious study, eventually turning to dark, dark forces. This resulted in his summoning of the Arch-Demon Marduk, who promised to destroy his rivals.
He did, but he didn't stop there. What Eldred didn't know was that Marduk was a being of infinite appetite, a monster who fed off the worlds to which he was summoned. With Jhera crumbling into nothingness beneath his feet, Eldred and Zyzyx fled into the Astral Void, eventually "washing up" in the world in which the game is set.
This world is ruled by five gods and their wizard-champions:
The player takes on a mission to champion for one of these gods. After each mission you get to choose another task, and thus choose to serve a different god (or the same one) for the next mission. As the game progresses and the gods factionalise in preparation for their war, the player begins to lose contact with the gods of whichever faction he has assisted the least, except if the player champions for Stratos, who is amorally neutral and self-serving and plays off all factions to his own benefit.
It is, however, shown in the fourth mission that Marduk has followed Eldred to this world and is conspiring to destroy it as well. His plot involves the creation of a cult centred around Ashur, a persona he has created for himself, and founded with the help of Jaduggar, the last centaur, who despises the gods after Stratos allowed his people to be slaughtered. The cult revolves around the idea that gods are pointless beings whose very existence is predicated upon belief in them, and that the people of this world should stop believing and thereby free themselves of the endless religious warfare their gods have inflicted upon them over the millennia. In fact, Marduk is merely aiming to eliminate all supernatural resistance to his ultimate destruction of this world.
In the first six missions, if you accomplish some optional objectives or meet a particular target which are hidden from the list of primary objectives (in some maps, simply win the game; in some others, you have to figure that out) a god will offer you a boon upon victory, be the god the one who gave you the mission or another one involved in the game, ranging from increasing health, mana, or speed, to increasing magic resistance, physical resistance, and health or mana regeneration of your wizard.
The player fights through a total of nine missions, each one rewarding you with new creatures and spells, and the tenth and final mission taking place in the present and being the final showdown between Eldred and Marduk. Depending on the player's choices in his narration of the tale to Mithras, Marduk reveals himself in a different way, either telling the Player to open their eyes, or chiding him for not grasping power. Also, the God which the player serves in the ninth mission,effects Eldred's decision at the end of the story, depending on which, the Player can choose to move on to another realm, or help rule and rebuild the current realm.
One of the unique enemies in the game is Marduk. Marduk is the only wizard in-game who does not require an altar, and as such cannot be killed directly and also permitting him to directly steal the souls of the Player's slain creatures. This is unique only to the final level of the game, in other levels however, where Marduk makes a scripted appearance, it is possible to locate his altar either through Meanstalk 'catapulting' or through Scapex. However, attempts to attack Marduk or desecrate his altar, (If found, a rarity as they are usually located in hard-to-reach places) will prove futile, as Marduk simply teleports away off the Map, taking the altar with him.
Scapex is an advanced level creation program included with the game that enables players to create their own singleplayer and multiplayer maps.
It is also possible to place an extra body of the player in a section of the map. However, this body is incapable of moving or attacking. Humorously, the game warns the Player of attack, and the killed body, does not resurrect, but simply disappears off the map.