If you are having trouble completing the Bioethics quest, you can refer to the Bioethics Quest Video Guide which is coordinated with the steps in this guide.
In order to summon a homunculus in Ragnarok Online, you will need to complete the homunculus quest, which is also called the Bioethics quest (you will also need to be an Alchemist or Creator as this is their platinum quest after all). This is a pretty easy quest if you have done it before. You just have to run around Lighthalzen talking to NPCs. Lighthalzen is in the Schwaltzvalt Republic, you can get their by taking the airship in Yuno.
After you finish the Bioethics quest you will unlock the homunculus skill tree. This skill tree consists of three skills; Vaporize, Homunculus Resurrection and Call Homunculus. Unlike the platinum skills for other classes in ragnarok online, you will actually have to invest skill points into these skills.
Now, on to the Bioethics quest:
1. Go to the Toy Store in Lighthalzen and purchase Geek Glasses x 1, and Grandpa Beard x 1.
2. Go to the Schwaltzvalt Republic Main Office (the large building in the top left of Lighthalzen).
3. Once inside head left and look for Reagen Baler. Speak with him while wearing Geek Glasses and Grandpa Beard and he will let you into the Laboratory.
4. After entering the Laboratory keep walking straight to the far side of the room and enter that portal.
5. Find Kellasus in this room, he should be in the top right corner. Keep talking to him until he keeps saying the same thing ("I'm sorry...").
6. Now find Skrajjad,(he is right below Kellasus). Talk to him, he will tell you to find Keshibien.
7. Now find Keshibien and talk to him. He will tell you to find Broncher in the Lighthalzen Hotel.
8. Go to the Hotel located in the center of town, just north of the Kafra. Broncher is in the room to the right. Talk to him until he keeps saying the same thing over.
9. Return to Kellasus in the Laboratory. He will ask you 3 questions, the answers are:
For iRO: Vaporize, Embryo, Homunculus Resurrection
For euRO: Sabbath, Germination Breed, Resurrect Homunculus
10. After you have successfully answered all three questions, talk to Kellasus again. He will still not tell you anything about the Homunculus.
11. Go talk to Kellasus's son, Koring. He is located in the house at the top right corner of Lighthalzen.
12. Go back and talk to Kellasus again. He will now teach you Bioethics.