I think it is more likely that a Necropolis would be like the Blood Moon Expansion; a small set - - but with lotz, LOTZ of cards like that one has.
As I've been on this board, I've come to realise that the 'balance' aspects of gaming in Talisman are pretty darn important. So I don't know if they could or would make the Necropolis too much like Blood Moon in other respects. FFG wouldn't put lunar events in this or other sets because there are folks who haven't and won't buy the Blood Moon, so that just wouldn't work. A future large or small set might not interface with a previous set like FrostMarch due to the same reason.
But a Necropolis small set could have its own dark themes and not rely on Blood Moon memes. So perhaps Zombies and walking Skeletons should be a big part. Some while ago there was mention of a Master Evil Lich; this would work.
I suppose to have real drawing power - and value, there should be at least one concept, or enhanced concept that is very important to Necropolis.
This should be a true, new way of using Dark and Light fate. I've seen a number of posters and posts, ideas etc that indicate 'paying' dark or light for various actions or situations, but I think this misses the mark.
The payment of either side of Fate should be marked somehow, and when a threshold is reached, a consequence must occur.
Gonna go crazy here (well as crazy as a 57 year old gets!)
Necropolis advances the idea of alignments, fate and DEDICATION to Gods, either evil, good, or indifferent to the fate of mortals in the land of Talisman.
Whenever any player lands for the first time on 'their' spot to pray (graveyard-evil, chapel-good) they either can or cannot 'dedicate' to their respective Gods (Neutrals can pick, but you can only hold one dedication at a time). Once you are dedicated, every time you pay a Fate you must place it, appropriate side based on your dedication or choose, on your playing area (or a new card in your area like quest or quest-reward cards?).
Let's say the threshold number is 3. ONce three Fate of either dark or light is paid, the threshold comes due. What could that be? ( I could go a number of ways or have them all even).
Possibly new decks, like the Dragon decks with differing encounter cards for each alignment (again neutrals pick their poison ). Like the Dragon cards there are cool objects or places, etc, but there are a lot of bad things too.
Another idea would be that you inherit a new ability or one time opportunities (luck!). Light side threshold: When you land at the Castle, roll a die: 1) you get an immediate extra turn. 2) Get a gold/extra gold (turning in Prince/ss), 3) gain a life. 4) take a purchase card or a stable card. 5) take a Quest reward card at random. 6) You do not have to turn in the Prince/ss at the Castle, instead they are your permanant compansion (unless other affects, spells abilities) and you heal 1 life automatically at any 'good' place you can pray at.
Whew. got myself going there. Well I have my own other ideas for Dark rewards, and I see different ways of doing this; reward decks or die rolls as indicated. I'll leave Dark Die Roll effects for someone else to speculate on?