Mammoth's grave is a monster that used to be a demon-type monster and then became a dinosaur-type monster.
Obviously, it was dark in the manga, but the card is Earth.
As a character who played an active part in Yu-Gi-Oh's ridiculous combos in Yu-Gi-Oh!
This is the card that played the leading role in the ridiculous combo called forced fusion combo lol!
I used it quite a bit in the manga, but the other monsters were so cool... I think it was buried a bit.