Development and mutation
When Lickers were introduced to the film, they were identified by the Red Queen as one of The Hive's earliest experiments. The production of the Lickers resulted in what the Red Queen described as an unstable development when the T-Virus was injected into living tissue.
After the special forces team had shut down the Red Queen's defenses, The Hive lost a considerable amount of power, allowing one of the Lickers that was in its confinement to escape, lurking within The Hive. It eventually killed Spence Parks, who was earlier bitten by a zombie and tried to cure himself with the anti-virus. As it continued to consume Spence's flesh, the Red Queen reveals that when it consumes fresh DNA from another creature, it mutates into a more enhanced form of Licker, describing it as "a stronger, faster hunter".
Pursuit of survivors and death
The Advanced Licker proceeded to track down the remaining survivors of the incident that had transpired in The Hive (which includes Alice, Rain Ocampo, Chad Kaplan and Matt Addison). It eventually caught up to them trying to escape The Hive using the train that is connected between The Hive and the mansion. The Advanced Licker killed Chad Kaplan and infected Matt Addison via a scratch to the arm from the outside of the train.
It then proceeded to break into the train in an attempt to wipe out the remaining survivors. Alice impaled its long tongue with the sharp end of a pole to the floor door of the train. As Matt attempted to open the doors using a nearby switch, Rain became a zombie from prior infection earlier in the film, and Matt was forced to kill her with a shot to the head.
Rain's body fell on the switch that opened the floor doors, and the Advanced Licker fell and was dragged on the train tracks with its tongue still spiked to the floor of the train. It was then burned alive by the fire generated by the electrical sparks of the tracks. Matt closed the train's floor doors, severing the Licker's tongue, and the creature was left to die on the tracks while Alice and Matt made their escape on the train.
The Advanced Licker possessed the same abilities as a standard Licker as far as being able to scale walls and ceilings and attacking with its long tongue. However, it was shown to be much stronger (and larger) than a standard Licker as it could break through steel barricaded doors with minimal effort. It showed greater resistance to fire-arms as one shot to its outer brain (by Alice) did not deter it at all from pursuing its targets.