New champion concept. One of lucians past partners

Initial concept. so ive been thinking how riot likes to occasionally throw in whole new concepts with their new champion releases. such as orne having unique items or kayn being able to turn into 2 different forms or even xayah and rakan having unique buffs when played together. so I was thinking of a champion that has a way to get around the respawn timer in a way that no other champion (as far as I know) can.

the lore. So I decided the best way to deal with someone who essentially cheats death would to have them hail from the shadow isles. I'm not entirely sure what his name should be so from now on I will simply refer to him as "my champion. His lore would be that he used to be one of lucians partners as they worked together to "purify" the world of the abominations of the shadow isles. During their assault on the shadow isles the 3 of them (Lucian, Senna and my champion) would eventually find thresh and while senna was killed and her soul taken by thresh Lucian was able to avoid such a fate as was my champion. however my champion did not avoid such a fate by fleeing or fighting instead fearing for his life he took the route of cowardice and made a dark bargain with thresh. Now a servant of thresh he is able to keep his life so long as he continues to bring thresh more victims for thresh to torture and consume.

gameplay. my champions main gimmick would revolve around his passive "dark bargain" which make it where every time he gets a kill (assists don't count it has to be a kill) he would gain a stack of his passive up to 10 stacks. Each stack would give him a few points of some offensive stat probably something like ad, attack speed, lethality or even potentially lifesteal probably lethality to make it more unique and distinquish it from the legend runes in precision. anyway the interesting part of this passive occurs whenever he dies. Upon death all stacks are consumed reducing his respawn timer by 10% for each stack. So if you have maximum stacks you would lose all the stats you got from your passive but you would respawn at your base instantly. Also I due to the fact that he has made a dark bargain with an evil force like thresh he is unable to purchase the item guardian angel because no angel is gonna wanna guard my evil champion.

TlDR: former partner of Lucian became partners with thresh in exchange for his life. everytime he gets a kill it reduces the time of his next respawn timer. cant buy GA because of it.