Plagued Hatchlings requires you to enter Scholomance and slay the plagued wyrmlings which dwell within.
Kill 20 Plagued Hatchlings, then return to Betina Bigglezink at the Light's Hope Chapel.
- Plagued Hatchling slain (20)
Their necromancers are breeding plagued dragons at the Scholomance, in the middle of Darrowmere Lake.
Go to the Scholomance and kill as many hatchlings as you can... before they get any bigger!
Well done, <name>! It'll be a long time before they can grow another clutch of dragons.
...At least, I hope it will!