Visit the NPC Wimmip in the TG Magic School. They are located in the bottom part of the training room, room 20. If you stand in Magic School of Tarsengaard [268,189] and talk to Wimmip she says
Wimmip:
‚Wow.. thanks a lot. I guess you will need more information about them then. I don't know where they are now, but I suspect most, if not all are trying to be with their kind, so look into places with other creatures like them. Here is the list of monsters that were lost, 1 of each: rat, goblin, puma, ogre and cyclops. If you kill them all please come back and tell me. Oh, and please, don't tell anyone about it!
You gained 35000 Attack, 35000 Defense, 10000 Summoning and 10000 Ranging experience
gotta kill one rat in rat cave on ip
one puma in the Elvaro Moutains
one gob in narlik
one ogre in PV in the ogre cave there
one cyclops in EP by the temple