It's maybe not a "catchphrase," but I think it would be funny(?) to have a Death Domain cleric who would constantly bring up the subject of death at inappropriate times.
"Oh, I meant to tell you, I ran into Jack the other day. He's not dead yet. Anyway he said to say hello."
"I love the autumn, it would be my favorite season to die in. Do you agree?"
"My mom, she's dead you know, used to love shopping there. When she was alive, I mean."
"Hi Rudy! I see that nobody's killed you yet. How have you been?"
"Oh what a lovely dog! Can I pet her before she dies?"
"Tell the chef that the pork roast was delicious! It didn't taste anything like a dead pig."
"Happy 67th birthday, Carl! How many more do you think you'll get before you die?"
And so on.
