If the opponent Kaalia attacked is no longer in the game when its ability resolves, you may put an Angel, Demon, or Dragon creature card onto the battlefield tapped, but it won't be attacking anyone and it won't be an attacking creature
Notably, casting a multicolor card will trigger two or more of these abilities, making Aragorn more efficient and rewarding for players using him in a color-heavy deck with lots of multicolor cards -- of which Tales of Middle-Earth has plenty
Law may still have the most infamous banned-leader legacy, but Enel is the purple leader defining the current competitive conversation
What can the cards be about then, in this context
That means not only do you get something back, but its immediately protected from most forms of removal
You can turn foes' stuff into Snow and keep growing your Owl