Mar-Vell is a Kree who, during the 1990s, resided on Earth under the guise of Walter Lawson. During that time, he mentored Carol Danvers and helped her understand her abilities.
Real Name: Mar-Vell
Portrayed by: Jude Law
From the Comics
In the comics, Mar-Vell was the first to have held the title of Captain Marvel.
After the Kree's first encounter with humans, Captain Mar-Vell is sent to spy on Earth and decide if it is a threat to the Kree empire. He adopts the identity of a recently deceased scientist named Walter Lawson, but occasionally dons his Kree military uniform to protect the people he's observing.
The first time he does this, people hear him incorrectly pronounce his name as "Captain Marvel". His job is made difficult by his jealous commanding officer, Colonel Yon-Rogg, his growing affection for humanity, and his fake identity's criminal past.
After aiding humanity several times, Mar-Vell is found guilty of treason against the Kree Empire and sentenced to death by firing squad. Mar-Vell escapes in a stolen rocket, but becomes lost in space. After drifting for 112 days, he is weak and on the verge of madness. He is manipulated by Ronan the Accuser and Kree Minister Zarek into helping them overthrow the Supreme Intelligence.
To better help them, Mar-Vell is given a new costume and enhanced abilities. After the conspiracy is foiled, Mar-Vell tries to return to Earth. On the way, he is hit by a blast of radiation that traps him in the Negative Zone.