Behemoths or dungeons spawning randomly in the wilderness that players could track just like meteors?
Maybe have several spawning at the same time with different qualities, players would be able to tell which one yields the highest quality materials. High tier players wouldn't snowball as much from winning all the fights at the highest quality event and it would give mid tier groups of players a chance to compete for precious resources by going after the lower quality ones while the strongest groups fight over the highest quality node.