So now the Lich in your Dungeon got a hobby... (Part 1)

Immortals have too much time on their hands

But not only immortals. Every intelligent-but-lonely monster/NPC in a dungeon should have huge amounts of free time at their disposal, be it dragon, (evil) wizard, vampire (well, vampires are also immortal, but they had to make the list), beholders, you name it. To have a hobby* is only natural. What follows is a list of recreational habits of those beloved monsters (and potential adventure seeds).

Roll 1d10 to determine hobby:

1. playing music: 1d8 for instrument (1 organ 2 piano 3 violin 4 zither 5 harp 6 bagpipe 7 contrabass 8 something very exotic (mouth organ**, sax, etc.); dungeon will have a room with the perfect accoustics, protected like a treasure; immortal creatures will compose own pieces (working on a masterpiece).
2. patron of the fine arts: will have 1d10 artists they influence, foster and protect, they not only have a lot of correspondance at their lair, but also first editions, rare paintings and 1d6 artists captive, to keep them for themselves; immortals will have a significant influence on the cultural output of a region (they also controll 2d10 publishers, theater owners, etc.).
3. correspondance chess: plays regularly with another powerfull and intelligent being, who would be pissed to loose his chess mate because of some group of adventurers; immortals will have 2d6 chess buddies and/or will ave very complex new rules for the game..
4. sculpting: 1d6 for material (1 wood 2 stone 3 ivory 4 skin 5 flesh 6 glass); will have all the necessary tools and 1d4 unfinished works lying around; dungeon will have a room exhibiting them and protected like a treasure (3d8 sculptures worth 1d20 x 100 each); immortal monsters will collect, too and their projects tend to be bigger/more ambitious.
5. painting: will have all the necessary tools and 1d8 unfinished works lying around; dungeon will have a room exhibiting the rest and protected like a treasure (3d8 paintings worth 1d6 x 100 each); immortal monsters will collect, too and their projects tend to be bigger/more ambitious, immortal monsters might have (1 in d6) a unique and brilliant technique (worth 1d100 x 100 gp per painting with the right buyer).
6. people watching: will have 2d4 scying devices and keeps taps of favourites on a daily basis; will take action, if something threatens the flow of the show; will have journals with detailed informations and analysis about the subjects; immortals will even try and controll/influence what's happening, like staging a play, etc..
7. architecture: this one really put some thought and effort into the environment he's living in; occupying ruined and old structures, the changes will be obvious and "modern" to an explorer (and potentialy more dangerous, traps will work 5 in 6 times, security is tough); if they build their own lair, it's perfectly build to the inhabitants needs and a work in progress (with areas closed as "under construction" and hired workers, constantly supervised by the creature); immortal creatures have a tendency to build mega structures; the dungeon is the price here, valuable (un)real estate for the adventurers to sell (or to live in, if you think about it).
8. :pit fights: traps near the lair of this creature will rather capture victims than killing them; the creature will have access to an arena; parts of the dungeon will be modified to hold a variety of captives and the personal to to take care of them; will have correspondance with slavers and every other group of people willing to capture and sell anything capable of fighting back; immortals will have very elaborate pit fight scenarios, with fights going on for days or even weeks.
9. human politics: killing this creature might topple kingdoms or lead cities into anarchy, will have a lot of correspondance with and incriminating evidence against those of higher social status; see 1d100 for number of controlled officials (1-10 local town, small community 11-20 two towns or one bigger town 21-30 small province 31-50 province with 1 significant city 51-70 a shire 71-80 a duchy/megacity 81-90 grand duchy/small kingdom 91-100 kingdom; hd as bonus on d100; immortal creatures also get their age divided by 100 as a bonus).
10. hunting: dungeon will have protected areas exhibiting a wide variety of trophies; the longer the lifespan of a creature with this hobby, the more elaborate the hunting techniques, up to actively searching for dangerous creatures or famous adventurers and planning hunts for weeks or even months (will have plans and contacts in his lair).

This list could be much more extensive, but I decided to make the first ten public now and will post another one as soon as I've finished them. I had 20 in mind at first, but the list of hobbies one could use for this is really bigger than that (courting, collecting, horticulture, brewing, you name it). Maybe 1d30? We'll see. 

* Wikipedia has a very interesting list of hobbies here. Strangely enough, sand castle building made the list, roleplaying games didn't. Very strange what counts as a hobby nowadays...
** Beholders love those...