There are 7 planes of existence, the major of which is the Physical plane, where all physical matter exists. In living beings however, there exists a soul; an entity that operates within a living being, and itself operating on the 2nd highest plane: that of the Astrals. In normal circumstances, the Astral plane is inaccessible save to those who have passed. Their physical bodies too old to function, the souls then retain themselves in the plane of Astrals. However, in the Ancient Times, a small faction of mages discovered the means of access into the upper planes, without harming themselves like so many before them had. In the Astral plane, they discovered a whole universe of the passed and they grew infatuated with their sudden discovery. They were enchanted and returned to the upper planes whenever they could. That is, until the day they joined the Astral Plane permanently.
What these mages had failed to discover however, was that without a soul to inhabit it, their bodies were completely defenceless, void of action, ability and meaning. An enemy faction, seeking to destroy all trace of the means of transplanar travel, took advantage of this, and bloodily massacred the lifeless bodies. Without a body to return to, the transported souls were stuck in the Astral Plane, unable to enact their own revenge. Save one. One of the mages had hesitated in releasing his fire upon laying his own eyes on her. Aleksyth's body only lay there before him, as if asleep. Quickly he hid her from the others' sight and vowed to return for her. Only, he never did. Upon returning for her, she was long gone. Immortal as she was, and the last of her preyed-upon faction, all she could do was run and for centuries, she did.
Millenia had passed, and using her own abilities to spy upon the doings of the changing world, she finally found the place where she could be safe, even if only temporarily; where else could she go? So for the first time in the years passed, she rejoined civilisation, and entered the Halls of the League.
"I have run for millenia, looked death in the eye thousands of times, survived on my own for eons. Do not think I will not survive a simple arena."― Aleksyth, Spirit of the Astrals
Though I realise the lore is extremely bad, highly cliché and patchy, my lores tend to be last minute. I put the concept together without the lore, as I do with all the concepts, haha. Anyway, the idea was that Aleksyth is meant to let out enormous amounts of power while always keeping an eye on the one thing that could end her. Though her body is fragile, her astral form is her only defence. It might make for HIGHLY interesting gameplay.
Check out my other concepts: http://leagueoflegends.wikia.com/wiki/User_blog:Asfidyll/Lyrene,_Daughter_of_Freljord http://leagueoflegends.wikia.com/wiki/User_blog:Asfidyll/Averyth,_the_Riftblade_Hunter http://leagueoflegends.wikia.com/wiki/User_blog:Asfidyll/Lexia,_Rakaar_of_Sylvis http://leagueoflegends.wikia.com/wiki/User_blog:Asfidyll/Kyel,_Arc_of_the_Storm http://leagueoflegends.wikia.com/wiki/User_blog:Asfidyll/Avaliel,_Call_of_the_Creed http://leagueoflegends.wikia.com/wiki/User_blog:Asfidyll/Savaras,_the_Pyromancer%27s_Halo http://leagueoflegends.wikia.com/wiki/User_blog:Asfidyll/Valenthis,_the_Soulweaver http://leagueoflegends.wikia.com/wiki/User_blog:Asfidyll/Tridon,_the_Archer%27s_Assailant