Demons and yordles are close cousins from the spirit world, almost like two sides of the same coin. Azakana and fae are smaller less psychical varieties of these spirits.
Demons feed on negative concepts like fear or addiction and often claim territory for themselves so they can eat consistently without other demons or other spirits interfering with their livelihoods. Since psychical races don’t exactly like being tortured or gaslit demons tend to play to their desires but this also means that they’ve found more ways to take down demons since they need physical beings to interact with in general.
Yordles on the other hand tend to stay in between worlds in the safety of bandle city. They meld and mold to whatever company they keep or environment they’re in. What keeps yordles alive is interaction. A forgotten yordle is a dead yordle. Since they can easily get affection and attention from their kin, the idea of feeding as a part of being healthy has faded from modern yordles minds. That’s why yordles can become rather sickly or aged in runeterra mostly because they don’t think to search for companionship. When a yordle is really elderly they tend to ask for a box to lie in. What younger yordles don’t know is this is just a really quick way of removing all stimulation so that elders can pass on quickly.