There are two achievements in the NW corner of the map:
This these are actually part of a three-part event chain.
Upon defeating the Charr, Fangstrom becomes a vendor for roughly 10 minutes. After that, the devourer event starts up 10 minutes later. You'll know that it's about to start when you see Fangstrom spawn by Gorrik and start talking to him. The Cattle Custodian achievement is awarded by not losing any cattle. Head west after the event to the Soul's Hearth point of interest which will be the next event to earn the Generation Gap achievement. Here you'll want to fight the full size Charr by interacting with them. They come running over periodically. You'll need to defeat 25 of them.
The Cattle Custodian achievement can be done solo or in a group. If doing it solo, you'll want to capture more than one devourer at a time and bring them to the collection point.
The Generation Gap achievement is probably best done with at least two players with each on either capture point. A single player will prevent a capture point from being lost regardless of the number of Charr cubs in it. What you want to do is ignore the Charr cubs and just wait for the larger ones in order to maximize how many you can defeat to progress the achievement. It really shouldn't take more than three event chain cycles unless you have people shooing away the Charr cubs.