Chatting about magic.
A logical calm necromancer, has been known to carry a book of ancient spells with him and try to grow in power. Has been known to raise armies of the undead as well as Bone Lords who are much stronger, smarter and powerful than regular undead.
Marthonis started his career as a young wizard at the service of the Twins during the siege of Marali. After their defeat, Marthonis studied necromancy from a book he would have stollen (the versions are contradictory here, and it is unclear whether he stole the book from Marali or from Brigobaen). He also became the leader of the Black Hand while the Twins were hiding. According to a letter from Varsha to her brother, the Alliance went underground at this time, fearing Marthonis' new experiments with the dead.
The necromancer was also involved in the creation of the Blood Lich; an experiment that did not go well for him. After that, he set his Bone Lords to eradicate all the elements of the Satel family, believed to form the Blood Cult of Gohoran.
Marthonis is unquestionably one of the most dangerous wizards in Oberin. However, he has helped Mirith defeating the Eye, and nowadays is even seen chatting about magic and the like at the surroundings of cemeteries. As long as he is not on a mission, that is. If anything stays between him and his quest for knowledge, he will not hesitate before releasing his Bone Lords against his adversaries.