I would argue that unlike burning metals (Preservation) and having a net gain equation (metal consumed, power arrives), the Aviars? seem to be a zero-sum magic like Ruin's (Metal contains power and slowly drains away from source 1, but is gifted to source 2 to a lesser degree). Bird eats food, parasite feeds off bird, investiture is created, and the birds use it. The birds themselves are infect with parasites which "grant" them the abilities. (Bird eats anyway, and if the bird begins to starve I think the abilities will continue until the point the parasite kills the bird or death from starvation after death of parasite) Kokre's abilities seem very much like a Copperclouds, while Sak's abilities seem like Lightbending, Atium burning, or maybe something we have seen Hoid do with smoke combined. If the bird can see future instances, showing them to others is outside of what we've seen so far in Mistborn (Atium visions), but similar to what we've seen Hoid do with Kaladin (Campfire Flute Storytime). My real question is... why the hell don't the worms get out of town if they can forsee danger... I don't understand why mistings can only burn some metals, you would think that they can either access leras based investiture or not, but it gets to be so specific based on not only the metal being used for access, but on the person.. So the birds resemble Stormlight more since the parasites seem to affect all birds of a similar type the same way, and the worms are all the same. Those worms/parasites in the worms seem so interesting... Does Lift have a parasite maybe ?!