Lady of Avalon Slot by Light & Wonder

The Lady symbol does two jobs at once, and that's the first thing worth getting straight. She's the wild, substituting for everything else on the reels, and she's also the scatter that pays from wherever she lands and counts toward the bonus. One symbol, both roles, in the classic "book" mould. Three, four or five of her anywhere hand you a fixed block of free spins, regardless of where they sit on the grid. The Lady herself is a dark-haired woman in white cradling a glowing full moon inside a gilded oval, and she's easily the prettiest icon on a board that runs through red, gold and blue royal cards, a rearing black Clydesdale, a sunlit castle, a closed red-and-gold spellbook, and a white-bearded Merlin scratching at a luminous quill.

Here's where it gets interesting, and where it splits off from the castle-siege machines Light & Wonder tends to build. The moment the bonus begins, the game picks one ordinary symbol at random and marks it as special. For the rest of the round, any time that chosen symbol lands and forms part of a win, every copy of it stretches to fill its entire reel, top to bottom, and pays across all ten lines as if the positions were adjacent. Draw a high-value pick and the reels can carpet over almost completely on a single spin. Draw a low card and the round plays flat. That randomness is the whole tension of the feature.

The Lady keeps working during the bonus too. Three or more of her on screen retrigger another set of free spins, and those retriggers stack, so a strong round can keep topping itself up. She won't expand like the chosen symbol does, but as a roaming mystical magic wild she still patches lines together, and the expanding special symbol handles the heavy hitting.