The Lost Rune is the prologue of SpellForce: The Order of Dawn.
The rune warrior Tahira had lived a calm live after the end of the Convocation. However her former master, Rohen, sent Caele to her because he had been looking for a special rune: The rune of the future Phoenix Bearer.
Said rune stone was supposed to be located within the ruins of Ankbrand.
Caele had been sent together with two companions, Joshua and Lev, but they were confronted with strong resistance from the local orcs and the other creatures. They were forced to retreat and thus Caele had been asking for help from Tahira.
Tahira headed towards the east and found Lev heavily wounded and thus healed him with her white magic. Lev stated that Joshua stayed behind in the south. Towards the south Tahira was able to learn the spell Fireball and to use it against the minotaur Gronz.
After she had defeated a skeleton and then used the gemstone gotten from it to purchase a human worker rune from the merchant, found Joshua.
He stood close to a human monument and told that the orcs and goblins were great in numbers and thus had to be dealt with a larger combat army. Tahira created several soldiers and built a huge base. She then headed out to the east and obliterated goblins and orcs and then was able to defeat Krong. With the rune now in her possession, she headed back to Joshua.
Joshua headed to the western portal. However lots of orc fighters appeared and attacked. The circle mage Rohen appeared and devastated the orcs with the use of his archfire magic. When Tahira gave him the future Phoenix Bearer's rune, Rohen thanked her. The prologue quest then ended.
All insights given by the narrator during the prologue are not mentioned here. Just follow the ingame description as told by the tutorial narrator.