Due to both canon (his Master dying in a way reminiscent of his teacher) and Tower events (his friends and his Masters getting sent back to their dead worlds), it's fair to say Lancer already has a lot of anger and will to die buried within him. The added dose of despair is gonna kick him into fully berserk riastrad territory.
When that happens, he'll spend most of his time fighting for Nyx in his warped state, making him to the heavy slugger of the team. He'll be too angry to tell who's who, but might hesitate in tearing apart someone he's really, really close to. Being angry all the time means he lacks his runes and will primarily rely on slamming into people with brute force or, if need be, exploding Gae Bolg. And what's more, given that he doesn't care about his own life or even victory, his attacks will be reckless. He'll just want to smash everything within a certain radius.
To summarize, a pure brute who might smash you into pieces, but wouldn't chase you if you snuck past him.
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When that happens, he'll spend most of his time fighting for Nyx in his warped state, making him to the heavy slugger of the team. He'll be too angry to tell who's who, but might hesitate in tearing apart someone he's really, really close to. Being angry all the time means he lacks his runes and will primarily rely on slamming into people with brute force or, if need be, exploding Gae Bolg. And what's more, given that he doesn't care about his own life or even victory, his attacks will be reckless. He'll just want to smash everything within a certain radius.
To summarize, a pure brute who might smash you into pieces, but wouldn't chase you if you snuck past him.