We all know that Lucifer became suspicious of Chloe's uniqueness when she proved invulnerable to his mojo, and as we've come to learn, her presence also causes him to lose his invincibility. This is a side effect of Lucifer's feelings for Chloe: his love for her lowers his defences and makes him vulnerable, leaving him physically able to be hurt. But in part one of season five, there's a lot of mojo swapping and losing powers going around.
Lucifer's invincibility returns in the final episode, allowing him to survive being shot unscathed, even when he's with Chloe. It could signal that he doesn't feel as vulnerable around the detective anymore, but it's more likely that as his relationship with Chloe solidifies, Lucifer feels less weak and uncertain. But Lucifer's powers always seem to suffer some sort of setback, will he only be invulnerable around Chloe now or will he lose it now that his father is back in the picture?