Allen borrowed the power of Ymir, and the original source of Ymir's power was a strange bug in a tree hole. This form of Allen is very similar to that of strange insects. Especially the bones growing on the back, there is no reference to the growth of human bones. So Allen became a skeleton.

The correlation is as follows

The benefits of bones:

1, first of all, you can ignore the attacks of many shells, because they are basically bones, and the probability of shells not hitting will increase.

2. A giant with only bones is different from an average intelligent giant. There is no "driver" in this part of the cervical vertebra. Faced with a huge body, they couldn't be sure whether Allen was in the skull. For Allen, this is very beneficial.

3. This form of Allen has super endurance, because there is no muscle consumption. After the giant, he can fight for a long time.