Mutant Year Zero: Road to Eden

As you explore the new zones found in the Seed of Evil DLC you will be contacted by Pripp. He will mention various sidequests that all deal with new enemies found in previous zones from the base game. You'll have to warp to them via the map and kill all of the new enemies to get credit for the quest. They're pretty hard to miss, but a couple of them are found in zones that the main DLC storyline won't take you through.

There are five in total. Here they are in the order that you can do them:

Found in Water Risers, back to High Road
Pripp contacts you near where you encounter Big Khan.
Encounter consists of Zone Dogs, Shaman, Hunter and Med-Bot. Shaman can summon reinforcements.

Found in Hall of Electric Coffins, back to The Sea Titans
Pripp contacts you near the entrance
Encounter consists of all robots. (Polis-bots, Med-bots, etc)

Found in The Under-Ark, back to House of Bones
Pripp contacts you near the entrance
Encounter consists of mostly organic enemies (Pyros, Hunters, Marauders, etc) and a Med-bot.

Found in The Last Stand, back to Spear of Heaven
Pripp contacts you near the entrance
Encounter consists of mixed organic and robot enemies.

Found in Valley of Steel, back to The Metal Fields
Pripp contacts you near the entrance
Encounter consists of mostly organic enemies and a Med-bot.