The Coin of Life
Lucas ambushes Alex Hade, Jade Wang, Jess Wang and Kylie Harper. He and Alex exchange words. He reveals that his forces have captured all the other Guardians except Sam and Darren, who later come to disrupt. The groups begin to battle, with Lucas taking on Alex. He tries to use the water against him, but it is firmly under Sam's control. Alex beats him easily, much to the surprise of everyone. Instead of killing him, Alex makes a deal with him, which Lucas is later shown to have kept. Alex respects him for this.
They meet again at the Louvre. When he sees Alex, Lucas shrugs, appearing to let Alex know that he kept his end of the deal. He takes part in the battle. He is one of many killed in the blast.
The Hunt for Parke
Lucas is mentioned several times by Alex and the crew. He is first mention when it is revealed that his death plagues Alex, who believes that it was his fault. Jade tries to convince him that it wasn't, but admits that Lucas was a 'good man for trying to honor the deal'. Alex appears to believe that Lucas didn't deserve to die.
Lucas appeared to be very cocky when he first met Alex Hade. Though he is also shown to be honorable, after keeping his end of the deal and in many ways thwarting Geron's plans in his refusal to go after Alex. According to Geron, Lucas was afraid of Alex.
Alex reaches the peak of his depression when he learns of Lucas' death, which indicates that he actually liked Lucas as a person.
Alex apparently wasn't very impressed or threatened by Lucas' appearance, being very lean and shorter than him.
Lucas apparently feared Alex, but tried to honor their deal. Alex, who was watching the aftermath proceedings at the Louvre spotted Lucas' body, then said 'that was about how far he watched before he became thoroughly depressed.' Alex expresses deep grievances over Lucas' death.