You Do Need power plug adapter while traveling from Eritrea to Ethiopia.

Here is Why You Need An Adapter

The outlet and plug type used in Ethiopia are C, F and G and in Eritrea are C and L. This is how they look like.

Eritrea

In Eritrea, outlets of type C and L are in use.

Type C

Type L

Ethiopia

In Ethiopia, outlets of type C, F and G are in use.

Type C

Type F

Type G