Dominion: Dark Ages

Shelters replace starting Estates in some games as described under Preparation, but they are never part of the Supply and cannot be bought or returned with Ambassador; they can, however, be trashed by effects that trash cards (and Overgrown Estate is a Victory card worth 0 VP). (pages 4, 6, 14)

Unless a card specifically says otherwise, a gained card comes from the Supply and is put into your discard pile; some cards explicitly change this (for example Armory gains to the top of your deck). (pages 7, 16–17)

If the Ruins pile is used it is part of the Supply: shuffle the mixed Ruins, include 10 per player, place the pile face down with the top card face up, and only the top Ruins can be gained or bought; Ruins are Action cards and may be played, and the Ruins pile being empty counts toward end-game pile conditions. (pages 5, 18)

Yes: a "when you trash this" ability triggers no matter whose turn it is and regardless of who trashes it, and the player who owned the trashed card is the one for whom the ability functions; these effects happen immediately after the card is put into the trash. (page 5)

If an effect expects to move or find a particular card but that card has been moved or covered up, the effect fails to move it (it "lost track"), but everything else still resolves; see the Procession/Madman example for how this can affect multi-step plays. (page 7)

Procession plays the chosen Action twice, then trashes it; any effects that happen when that card is trashed resolve before you gain the new Action, and you must then gain an Action from the Supply that costs exactly 1 more (gaining fails only if no such card exists). (pages 16–17)