A tyger is a large animal that is predominantly orange with black stripes.
Tim Ross faces Maerlyn, transformed into a tyger
It is a descendant of the feline family and looks like a large cat with sharp teeth and claws. It is similar to the tiger of our level of the Tower, save the spelling of its species.
The only appearance of a tyger in The Dark Tower Series is in The Wind Through the Keyhole , when Tim Ross finds Maerlyn transformed into one by "one far greater than he of the broad cloak." Maerlyn tells Tim that he was tricked by an emissary of the Crimson King that came by his cave posing as a wandering peddler. He goes on to say that even though he was more powerful than the deceiver he fell victim because he was drunk.