Cactus Game Design Message Boards

Chamber of Angels:
Set this fortress aside. If holder’s angel is being discarded, place it here instead. After two turns, return Hero to the top of your draw pile.

Tartaros:
If your demon is discarded or captured, you may hold it here instead.  If your demon wins a battle, you may underdeck a demon from here.

Fishing Boat:
Set this aside. Each upkeep, you may place a Hero from here beneath your deck to draw X or to give your disciples access to all Sites this turn.

It reads more like Chamber of Angels than Fishing Boat to me, so I'm pretty sure you can't just place demons there.

I guess I don't understand the difference between them if they have the same identifier. Tartaros and chambers' don't sound like exclusive abilities.

You can only add or remove from a fortress at will if it does not explicitly say how/when they can both be added and removed:

If a Fortress with a hold​ability does not describe how cards are both added and removed then you may add or remove cards during your preparation phase.

Both Chamber and Tartaros describe both how cards enter and how they leave.  Therefore, you cannot just add them at-will.