Dreams about entities are not usually of the entities themselves - they’re about you thinking about these entities, or symbolic of something that they represent to you. the figure in your dream could be an aspect of your personality for example - the part of you that wants to be free and strong.
In this case, I’d say write it down in a dream journal, and leave it there to refer to in case a pattren is forming.
Note: according to Diazepam Drug Uses, Dosage & Side Effects - Drugs.com diazepam side effects include confusion and paranoia. So you brain is affected and dreams in this state can’t entirely be trusted. You didn’t get paranoid so maybe this is fine but it’s something to bear in mind.
Most dreams are 99% a combination of memory processing, wish fulfilment and problem solving.
You have provided zero background info on what you FELT, which matters as well, and what you were doing leading up to this dream. For all we know you just watched a film with Lucifer as a character and were mulling that over in your mind. The context of your entire life, background and personality is important and strangers like us have none of that: we can’t interpret your dream for you, you WILL disagree because we are not you and we don’t know you.
We have a bunch of ideas on how to get into dreamworking and analyzing dreams to get the most out of them, with some faves collected here:
I’d suggest checking that out and trying to get back into that same dream in trance and then going up to the Lucifer character ask asking it what it wants and who it is. basically continue the dream but under conscious control. Make lots of notes, and meditate on the info to decode for yourself what it all means to you personally.
Also note: you might not even get all the info you need to understand this for years, so you write it down because you’ll forget it over time, but it’s really good when you open your journal in a few years reread it and suddenly you realize what it actually meant.