So for my birthday (well, the night before, but going into the morning of) I had a really great session of D&D with my party. I came away with a smile on my face, and that's always great.
Partially it was because of a good fight - the party encountered a feature of the land in which they find themselves, called a Darkstorm, where undead and demons assail them. I decided to ditch my randomized list and instead pick an appropriately creepy creature from Volo's Guide to Monsters called a Spawn of Kyuss - a zombie-like thing filled with burrowing worms that can infect people (none of the players got hit, but a couple of NPCs they were guarding did - thankfully for them, the Paladin was ready with Lay on Hands to cure diseases.) Everyone got to do something cool during the fight.
The best part, however, was when I had them go into an Outer Plane of my own devising (I muck around a lot with D&D lore, though if I get into serious trouble I'll just make this a subsection of the Nine Hells) called the Oubliette, where they were trying to secure the release of a prisoner who had knowledge of the fortress they had just taken. As I had planned, a Bearded Devil appeared to try to stop them, but thankfully I trusted my instincts (and my battle fatigue after a protracted Darkstorm fight) I decided to play up the lawful, and thus bureaucratic nature of devils.
The Bearded Devil, who I named on the spot Kanameir, talked with the wizard in the party about securing a prisoner release form, which could only be done by proving the demise of the fortress' former commander and convincing him that the wizard was the new commander. The wizard rolled three natural 20s in a row - first to get the fiend to talk to him, second to know it would not be a good idea of ignore the devil's instruction to wait while he did hours worth of paperwork, and third to sign with a fake (ridiculous) name that, with a Deception check crit, he pulled off.
So now this party member not only has a friend in the infernal bureaucracy, but also secured the ability to house up to five prisoners within this horrific dimension. (He's True Neutral, so I don't think he'd have qualms.)
Anyway, as I said before, my quasi-new-years resolution was to allow for more non-combat encounters as the players saw fit, and this early example was a huge success.