Possession

For The Syren and Unforgiven, this is not functional errata, just a clarification. For Portal Rescue, this is a slight functional change to its interaction with cards like Possession. Previously, you could use Portal Rescue to re-play a card you took with Possession and retain control of it, but under the new wording this would give it back to its owner.

414.5. Players who drop from limited format tournaments own the cards that they correctly have in their possession at the time of dropping, including unopened packs.

703.4.a.4. A player's deck is the incorrect deck size. See 402 for more information about deck size. (Examples: A player misplaced a card, a player forgot to shuffle their banished cards back into their deck between games, a player's deck has an extra card or is missing a card due to an effect like Possession from a previous game.)