Boggle is a game involving 16 six sided dies with letters on them, which players shake and then use to make words. What is the only letter in a standard Boggle set that appears in lowercase?

The first new player to comment on the website with the correct answer wins a free drink at their next iQ Trivia quiz.
I know this one with certainty, but since I’m in the wrong state to claim the free drink at iQ, I will leave it open for the next player!
That’s very magnanimous of you.