So. Wait. I thought Lissandra was Ashe's sister or something?
Sibling rivalry.
Freljord has become a land of endless conflict since the "War of the Three Sisters" broke out. Even though Freljord already has a sovereign, tribal leaders still fight for it bringing with them their tribes.
The Winter's Claw tribe is led by the ferocious Sejuani. When she was born the tribe's mystics foretold that she would be Freljord's sovereign and she has held on to that prophecy to this day. On the day of her twentieth birthday, Sejuani declared to her tribe that she would lead them to war against the other tribes for the conquest of Freljord. She has since been attacking village after village, pillaging what resources the village had left and sparing those who wished to join her army. One of her more notable accomplishments was the forging of an alliance between the Winter's Claw and the new Ursine leader, Volibear.
The Avarosan are those whom are loyal to Queen Ashe. Unlike the members of the Winter's Claw, they are more peaceful and focus more on agriculture than on combat, though they are still very much capable of defending themselves. Ashe's rise to power began when the princess of the Ice Dervish, Lissandra, swore fealty to her. She then began an alliance with Tryndamere, the high chieftain of the barbarian tribes. Anivia soon after joined Ashe in her campaign to unify the tribes as both share the same beliefs. Eventaully, Freljord ascended to city-state status and Ashe as their queen, Tryndamere as her chosen king and league champion, Nunu, as the emissary for the League.
The Frostguard can also be considered a seperate faction from the Avarosan because of their leader, Lissandra. According to her League record, Lissandra is in fact the Ice Witch in disguise and that she has corrupted the once benevolent guardians of Freljord into her twisted minions, although the Freljordians still believe that they are still the ancient guardians that have protected Freljord since. Also, in Trundle's League record, he had made a deal with the Ice Witch. It states that, in exchange for her ice club, he promised her the fealty of the trolls.