Unown L can use any attack from any Unown in play (both yours and your opponent’s). (You still have to pay for that attack’s Energy cost.)
[P][C] Hidden Power
Search either player’s discard pile for up to any 2 cards, show them to your opponent, and put them on top of that player’s deck in any order you like.
Shaped like ancient writing, it is a huge mystery whether language or UNOWN came first.