I Will Take It 15G
Capture a ring with Frodo in a ranked Capture the Ring match.

How To
Combined with "Rings Of Power" achievement: To win a Capture the Ring match, you'd need to pick up the Ring, and deliver it to a required destination. After you successfully deliver two rings, you'll get the chance to play as a Hero. The only time that you can play as Frodo is in the Shire map, and you must be on the "Good" side. Choose to play as him, and then deliver the final ring to win the match to unlock both achievements.

Unfortunately, you can't choose which map to play on. The maps cycle through themselves. So after you get it, continue playing this mode through the rest of the maps until you get the Shire again, and help your friend with it.