I was actually unprepared for the game jam and made lots of plans over the weekend. But Friday morning I woke up, saw the post by 
Theme analysis
I always spend a good time on trying to figure out what the theme means, what different meanings it can have, and possibly ask some other people what it means to them.
The first thing I got was the song titled "into the unknown" from the garden over the wall. If you haven't watched it, I recommend it. It's a very nice piece of art.
Other thoughts I had were lovecraftian horror, non-euclidean geometry, 4th dimension, fear of the dark and the very obvious exploration.
Asking on discord I got a response of "the blank page" when an author is faced with infinite possibility, and is about to write, and nobody knows where it would go, not even the author. While I did not go with that specifically, it did inspire me to look in the storytelling direction.
Lovecraftian horror
There isn't anything quite as unknown as Lovecraftian horror, discovering all the terrible things that would drive anyone insane. I decided to write an interactive novel, but I didn't want it to just be a choose your own adventure, I wanted to to have some kind of game mechanic to it.
So I added time travel.
My initial idea was like so:
The story begins as our protagonist wakes up in an apartment in south tel aviv, slight hangover from the night before, and goes out into the world. Strange things keep happening throughout the day, growing further and further from reality, until an Ancient one awakens and devours the world.
At that point our protagonist wakes up again in their apartment in tel aviv, remembering some of the events that occurred during the previous iteration, but not anything specific. Since the player will undoubtedly remember it very clearly, I will randomize the events every time they restart, so they will feel like the protagonist felt, a combination of known and unknown.
To keep me from having to record actual information gathered by the player, I would take a page out of Fantasy Flight's book and use abstract clue tokens to signify the progress of uncovering what is needed to stop the Ancient one from awakening.
I considered having two separate types of clues. Clues that are lost between iterations and clues that remain between playthroughs.
I also considered having a sanity meter, slowly driving our protagonist insane as they die and reincarnate in horrible ways.
This all proved way too much to do in what would be about 24 hours of actual work, with all the other things scheduled. Having multiple sections of story all able to interconnect and all drive to uncovering the location of the ritual. Too much.
For a while, I tried to make a simplified version, something along the lines of a grow game. The player would have to visit all of 7 locations in the correct order to get to everything in the right moment to be able to stop the ritual. I started with mapping out the locations I wanted the protagonist to visit, here is the last iterations of locations, with some notes as what would happen there at what time:
1 Florentine bars - [1] Strangeness (Beach/Market/Central Bus Station/Synagogue)
2 Beach - [2] Disturbance in the waters (Jaffa Port/Clock Tower/Central Bus Station)
3 Central Bus Station - [2] Doomsayer (Jaffa Port/Beach), [3] Someone strange gets on a bus (Synagogue/Carmel Market).
4 Carmel Market- [4] Strange Peddler (Talisman).
5 Synagogue - [2] Golem alone death, [5] Golem and a Rabbi (Word of God)
6 The clock tower -
7 Jaffa port - [7]
8 Stairway into the abyss
I then realized I needed a clear timeline for the antagonists so I can have the protagonist disrupt them:
1 The aurora borealis that can be seen from the beach is the first mark of the coming of the leviathan.
2 The cult of the leviathan sees the aurora and take the busses from central bus station to the synagogue
3 The cult gather at the synagogue, after the regular prayer hiding among the hasidic jews.
4 The cult forms the great golem and send it to the clock tower
5 The golem tilts the clock tower pointing it towards the aurora
6 The cult open the stairs into the abyss
7 The cult gather in the abyss and the Leviathan arrives.
At this point, I started feeling rather lost, and decided to go with a different idea, which I will cover in part 2.
Learn from failure
Writing a plot is hard. I've never actually written a real plot, all I've ever written are ideas, conveyed in short stories. This story needed more meat, and I had no idea how to tackle it properly.
I still really like both ideas, the grow style game with a story, and the randomness to simulate the confusion of the protagonist, and I hope to have an opportunity to explore them.
If I want to have an ambitious game jam, I need to clear my schedule.
The grow style game along with the time travel allows me to make it so it is not possible to solve from the start, and only possible to solve on second or third playthroughs, by forcing the player to reveal locations in an order that will never result in success.
Into the unknown is a really tough theme, and while it can be tacked onto almost any game, it definitely inspires creativity. I like it.
Borrowing from environments I know, like tel aviv and Judaism did help.