Kebbel recently signed up to play a character called Vanessa in the CW series.
Lanter has now told Entertainment Weekly that Vanessa is a mysterious young woman.
"She's this girl who we're not really sure who she is yet and it'll take several episodes to figure out," he said. "She may be Liam's next love interest. It's going to be fun. It's kind of a mystery."
Lanter also revealed that the fall finale will end with a "huge life or death situation with Liam".
He teased: "We're not really sure what happens to him or if he returns, how he returns."
90210 airs on Tuesdays at 8/7c on The CW.
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