This is a Giant.
These mobs only spawn in the dark like skeletons. However, unlike most mobs they can survive in the light. You won’t find these mobs easily. They are also not hostile unless you attack them.
As seen on the picture above they are very big. They are also very strong and have a lot of health. However, they are big so you can easily trap them.
The Giant drops a Giant Bone.
Giant bones can be used to create bloody giant bones. These bones are used to craft Bone Spears.