Gnar was added to the Freljord region just recently with the Lissandra/Vel'Koz Void origins update
Before that he was a Runeterra champ which means he travelled around going anywhere doing anything.
Old Lore:
Gnar is a primeval yordle whose playful antics can erupt into a toddler's outrage in an instant, transforming him into a massive beast bent on destruction. Frozen in True Ice for millennia, the curious creature broke free and now hops about a changed world he sees as exotic and wondrous. Delighted by danger, Gnar flings whatever he can at his enemies, be it his bonetooth boomerang, or a nearby building.
A primitive yordle born millennia in the past, Gnar is playful, diminutive and cute until his occasional bouts of anger transform him into a massive, violent, and destructive beast. Trapped within a glacier of True Ice, Gnar was frozen for an age before he broke free, emerging to find the world much changed. These new, exotic realms only ignite his delight and curiosity, for where most fear danger, Gnar pounces to meet it head on.
No mention of Freljord even though True Ice is mentioned, back then True Ice could have just occured naturally anywhere it was cold. Now things are more set in stone and that Rengar/Gnar story is 100% non canon.
That story in the jungle is a Rengar story and one that may get axed when Qiyana hits live servers in 9.13 and Rengar gets his lore rewrite. Mordekaiser just got his old story deleted and Scathlocke has expressed his interest in doing some "clean up". For example the Vastaya lore page still references The Great Void War which is now non-canon.
