The 6 Lord of the Rings actors here also portrayed characters in the Marvel Cinematic Universe film franchise. Take the index for their MCU characters gives the answer CASTLE.
LOTR character Actor MCU character Index Letter Thranduil Lee Pace RONAN THE ACCUSER 10 C Tauriel Evangeline Lilly HOPE VAN DYNE 6 A Smaug Benedict Cumberbatch STEPHEN STRANGE 1 S Bilbo Baggins Martin Freeman EVERETT ROSS 6 T Gollum Andy Serkis ULYSSES KLAUE 2 L Galadriel Cate Blanchett HELA 2 E