I am a Turtle.
Based off of Kevin's concept of a nemesis where only one player knew a face down status card.
Aeon's End concept: Fateweaver
Unleash: Play the top card of the Fate deck. Remove 1 power token from each Fate card you control.
Fate pile with 3 cards face down.
Any damage dealt to Fateweaver is reduced to one.
Fateweaver cannot be dealt damage unless ‘Hope’’ is face up.
Any player during their main phase may pay 2 charges to draw the top card of the Fate deck.
Any player during their main phase may discard a prepped spell that costs 3 or more: Look at the top card of the Fate deck. You may place it into the bottom of the fate deck.
Hope: Power 2. Place this into the bottom of the Fate pile.
Destruction: While this is in play, all prepped spells gain ‘Cast: destroy a card in your hand’. Power 1: Gravehold suffers 3 damage. Shuffle this into the Fate pile.
Despair: While this is out, it costs 1 more charge to pull a card from the Fate deck. Power 1: Any player loses 1 charge and loses 1 life. Shuffle this into the Fate pile.
Will add nemesis specific cards later.
I've had a bit of time to brew on this, so here are my thoughts on the current iteration.
It's worth noting that 'hidden information' as a mechanic generally refers to mechanics where one player has information that another has. In this case, it doesn't really apply - 'not knowing which card is next' is a style of randomness, and revealing that card is a type of randomness mitigation. That already exists in a few scrying cards, so it's not really the 'different style' that a hidden information mechanic would be.
I think the goal here is to have the 'core' be a boss with a set of 'states' that you want to prepare for, and specific windows of opportunity to do certain things (usually either attack or prepare), and encourages appropriate setup for that time. However, this doesn't really do that right now.
Right now, the main issue is that you're putting out multiple powers, each with very short durations. It's well within the realm of possibility for people to prep spells, then completely miss that window due to a bad shuffle. Even if you did stack things up to your benefit, it still depends on the nemesis unleashing in a way that doesn't mess you up - and the variability of that is also incredibly high.
The states also aren't very 'unpredictable' or 'hidden' - with only 3 cards in a face-down deck, there's not actually that much variation. Given the high price you've set to both scry and play an individual card, it leads to situations where it's simply not worth scrying/forcing cards out in comparison to just letting the nemesis action. Considering when you have to force cards out (Main Phase) combined with the volatility of the unleash, and you mostly end up with cards getting spat out and resolving too fast to act. It's inconvenient to potentially draw and shuffle twice every "Unleash Twice", and quite possibly do more if certain powers/minions are in play. It would likely be better to aim for a thicker deck, with shuffles only triggered once the deck empties.
The last issue is that the damage reduction appears incredibly arbitrary here. When all damage is reduced to 1, there's very little reason to bother saving your big spells - you're still going to need to throw a lot of spells regardless. I'm not sure why this has 'damage to 1' on top of a secondary defense already - it seems more forced than necessary.
The core idea is interesting, but a lot of specific mechanics could use some cleaning up.