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All the effects that Special Summon the "Swordsoul Token" apply the restriction that the player cannot Special Summon monsters from the Extra Deck except Synchro Monsters while the Token is on the field, in order to prevent abuse with other Extra Deck Summoning methods

Winters card drawing ability is also easily abusable

Personally, not a big fan of Unexpectedly Absent, but it should be mentioned nonetheless because it can be useful in the right deck

Conclusively, the rarest common Pokmon TCG card is (drumroll please) red cheeks Pikachu, from the original 1st edition and shadowless printings of the very first English TCG base set