In the description of Ingol Island, according to Tibia.com, that Doctor is rumored to be Professor Maxxen or perhaps another unknown Doctor.
On the other hand, said island acted as a bridge between Roshamuul and Marapur in the past, until a cataclysm (probably the same one that caused the destruction of Roshamuul) separated these islands.
Since the dawn of humanity, this island served as a meeting point for pirates and smugglers, one of the most notorious being the pirate "Destan De'Brue". His enemies, upon reaching the island, found a destroyed ship with charred and mutilated people. Since then the Island has been feared by people.
As for the quest itself, we learn that a priest named Ysbasra sends us on a mission to that island to find her lost brother. In that place we have to complete certain tests to be able to access Dr. Marrow's last room, to fight him and complete the mission.
However, once the mission is finished, we can find a document in Ysbasra's tent (now she is no longer in the tent) where said document tells us that we were deceived by Ysbasra and she took advantage of this situation to steal the research done by Dr Marrow.
In this document, we are also specified that she belongs to the "legion" or organization called "Shiron'fal", in which she explains that the Dr. did not want to cooperate with the legion, so they decided to steal said research by force.
Interestingly, also in that document is mentioned that the boss Death Priest Shargon, former member of the Brotherhood of Bones and current member of Shiron'fal, is looking for relics in Oramond (the Blood Grail). Maybe we still need to use that item somewhere... maybe on this very island.
As a final comment, I must say that the content, being still so new, can hide much more information and connections with other NPCs and places. But so far, the connections we see are the following:
Dr Marrow- Shiron'fal (Death Priest Shargon)- Pirates - Roshamuul-Marapur.
Well, and we also found some boots in the island that also can be seen in Dawnport. I suspect it also has to do with Shiron'fal and obviously pirates :P
Sources:
www.tibia.com
The Craddle of Monster quest.