The Mahjarrat are powerful creatures in the game RuneScape. They are not entirely immortal, but nearly so. Look here for more details: http://runescape.wikia.com/wiki/Mahjarrat
No, it is just a made up names for spirits that follow the god Icthlarin.
Seven. There used to be six; one was added as part of the storyline of the "Ritual of the Mahjarrat" quest.
There is a history section of the Runescape website, but this time I will place some text here:uring the Second Age, Zaros had almost complete control of the world. The areas that are now the Wilderness, Northern Misthalin, Northern Asgarnia and North-western Morytania, formed the greatest part of his kingdom, where many great fortresses and cities were constructed. When he was betrayed and defeated by his Mahjarrat general, Zamorak, the Second Age ended and the other gods could now begin ruling without interference. However, many gods, the most significant being Saradomin and Zamorak, wanted complete control. After Zaros' defeat in single combat, Zamorak quickly set about to rounding up his remaining loyalist followers, and destroying his fortresses and cities. The majority were destroyed quickly, but Senntisten held out for many hundreds of years. The war escalated as other Gods, seeing an opportunity attempted to seize control of areas that had previously been Zaros, since Zamorak was unable to efficiently conquer and maintain his holdings, due to the speed with which he acted. The war escalated further, and by the time of the Fall of Hallowvale, almost the entirety of Gielinor was in chaos. The gods, at the time, could directly interact with the world, which caused destruction far beyond any seen before or after the wars. During the wars, countless civilisations, races, and animal species disappeared. Many were destroyed, while others hid themselves or went under drastic changes in order to survive. Much of the world itself went under drastic changes, with much of the land being ruined or reformed. Many of these changes were so catastrophic that they continue to affect RuneScape, even today. In fact, the entire world was on the brink of destruction when the fighting awoke Guthix from his sleep. Upon the end of the First Age, Guthix went into a deep slumber that stretched over many millennia. When he awoke, it found the world in ruin. It was so enraged that he instantly demanded that the gods stopped fighting their wars on RuneScape, and to continue to hold influence only through their followers. Most of the gods left RuneScape, although they continued to watch over it and hear the prayers of their faithful. It was at this time that the Third Age, which had lasted approximately 4000 years, finally ended.