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

Here is Why You Need An Adapter

The outlet and plug type used in Eritrea are C and L and in Nigeria are D and G. This is how they look like.

Nigeria

In Nigeria, outlets of type D and G are in use.

Type D

Type G

Eritrea

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

Type C

Type L