Marcello's gift allows him to immediately know whether a human or vampire has an extra gift; he'll be able to know how strong the gift will be and what type it will be. He does not need contact with the other person, he only needs to look at them and he'll know.
Also, his gift is so strong that when he looks at a human, he can know every possible gift that his/her traits will produce when they become a vampire, but the strongest type of gift which will be manifested is the easiest for Marcello to identify. He is also able to identify if a Quileute will be a shape-shifter.
He can also use his gift to let people know what they need to do to train and master their gifts.
Limitations[]
Like the majority of vampire gifts, Marcello's gift is mental, and so he can be blocked by Bella and Alessandra's ability to block mental abilities. However, differently from the other mentally gifted vampires, he seems to be able to actually feel the effects of Bella's gift, instead of being blocked out.
History[]
Orgin[]
As a human, Marcello was already able to identify the gifts of other humans around him, though he had to concentrate very hard to do so.
Post-transformation[]
"I looked for people who would be extremely gifted vampires, but would not use their gifts for evil."
―Marcello
When Marcello was changed, his ability manifested and became even stronger. After years of being alone, Marcello began searching for people who would be extremley gifted vampires, but would use their powers for good and not for evil, like the Volturi.
When he meet Eleazar, they both realized that Marcello's gift was much more stronger.
Similar Abilities[]
Eleazar
Eleazar's power is to sense whether a human or vampire has an extra gift and identify its type and strength. His gift isn't as strong as Marcello's.
Maggie
Maggie and Charles' gifts of lie detection allowed them to determine if someone they converse with is telling a lie, similar to how Eleazar can detect other people's powers.
