Tahm Kench v. Yordles
The Allies/Rivals system on champions' lore pages are some of my favorite pieces of world-building; they can give you a quick glance as to where the character fits in the world while providing additional extra-textual information.
Tahm Kench is allied with Aatrox, helping establish the already-confirmed notion that he is some ageless horror, a force-of-nature-type villain. However, his set of rivals is more perplexing; to be The River King's rival, all you have to do is be a yordle (unless you're Veigar, with whom he seems to be cool). He either hates the yordles, or the yordles hate him. Or both.
What could be the reasoning behind this rivalry? Are the little guys generally too pure-at-heart to succumb to his temptations, leaving him bitter? Or, perhaps, did Tahm corrupt a citizen of Bandle City, never to be trusted there again? Whatever the reason, this is an interaction that I really hope but do not expect for the lore team to explore.