Siegecraft is Beleaguered Castle with one free cell added, and it is the gentlest game in the open castle line. The four Aces are placed on the foundations before a card is dealt, so every suit is open from the first move; the remaining 48 cards go face up into eight piles of six. The tableau builds down by rank regardless of suit, one card at a time, and an empty pile takes any card. Beside the board sits a single cell that holds one card and gives it back whenever you want it. Free in your browser, no sign-up.
Goal: build all four foundations from Ace to King by suit.
With every suit open from move one, the game is about feeding the foundations without stripping the hosts you still need.
Siegecraft appears in the PySol Fan Club collection as Beleaguered Castle with one reserve square, and Wikipedia's account of the Beleaguered Castle variants describes it in the same words: it "adds a cell to move out a single card", making the game easier, and "the cell can only accommodate one card". That is the entire difference, and it is enough to change how the board is dug.
Its twin here is Stronghold, which adds the same single cell to Streets and Alleys instead, leaving the Aces buried. The pair are the clearest demonstration in the catalogue of what founding the Aces is worth: identical cells, identical building, and an opening problem that exists in one game and simply is not there in the other.
A note on the loss message, or its absence. The open castle games without cells can prove that a position is dead — with no stock and nothing hidden, a search can enumerate every future. Add a free cell and that proof stops being useful: while the cell is empty almost every card has a legal move into it, and while it is full that card usually has one back out, so a board is hardly ever fully locked. Siegecraft therefore does not announce a loss, and this page would rather say so than have the game claim a verdict it cannot support.
For the same board without the cell, play Beleaguered Castle; for the cell with the Aces buried, play Stronghold.
One free cell. The Aces are founded before the deal in both games, both lay out eight piles of six, and both build down by rank regardless of suit one card at a time. Siegecraft simply adds one square where a single card can be parked and later retrieved, which makes it noticeably easier.
Where the Aces start. Siegecraft founds them before the deal, so all four suits are open immediately and the piles hold six cards each. Stronghold leaves the Aces in the deal across piles of seven and six, so digging one out is the opening problem. Both games have exactly one cell.
One. While it holds a card it refuses every other, and that card can be played back to the tableau or up to a foundation at any time.
No. Only the top card of a pile moves, one card per move.
Yes. They are taken out of the shuffled deck before the columns are dealt, one to each suit's foundation, so the deal is 48 cards across eight piles of six. Because they are lifted in deck order, the same seed still produces exactly the same board.
Because with a free cell it almost never can. A cell gives nearly every exposed card somewhere to go, so a board is rarely completely locked, and a game that announced a loss it could not prove would be worse than one that leaves the judgement to you.