He is known as "Mario Greymist". "Greymist" might possibly be due to his use of a spell that produced a grey mist of sorcerous energy in the vicinity of the Imperial Orb which allowed him to assassinate Tortaalik, the last Phoenix Emperor before the Interregnum. Due to the timing of this assassination, he helped to precipitate Adron's Disaster.
Another interpretation for "Greymist" that Vlad Taltos relates is that it comes from Greymist Valley, located just above Deathgate Falls — Mario being so named for all of the people that he, during his highly successful career, has sent there. It is unclear which explanation is the more accurate. Since by Paarfi's account, Mario chose the mist's color himself, they could also both be true.
By Paarfi's account, Mario is a non-descript Dragaeran male who would blend into any crowd with hardly a glance. This of course does not include Aliera e'Kieron, who (again, according to Paarfi) found him stunningly beautiful (unsurprisingly, Mario reciprocated this attraction). Paarfi's account is that Mario and Aliera first met and became lovers as Mario was fleeing from his abortive first assassination attempt that he had made on Tortaalik.
As shown in Dzur, Mario appears to be alive and well, and still in touch with Aliera, though appearing strangely old. According to Paarfi, Mario was born circa 105 before the Interregnum and should therefore be about 600 years old at this time. Yet Vlad estimates his age as "over twenty-five hundred years".
In addition, Vlad describes Mario as having a round face, similar to a Teckla, although unlike a Teckla, Mario does have a noble's point. He generally looks like a friendly and somewhat elderly merchant.
Mario's whereabouts are generally unknown and he can only be hired via his contact, who is secretly Kragar. This relationship first started about 90 years prior to Vlad's time. Once Vlad was informed of this by Mario, Vlad requested, via Kragar, that Crithnak be assassinated, which Mario carried out.
Generalizing from the killings of Tortaalik and Crithnak, Mario appears to prefer to sever the spinal cord at the neck when he performs a permanent but non-Morganti assassination, as opposed to Vlad's preferred method of a dagger through the eye.
- See also Speculation:Mario.