You Do Need power plug adapter while traveling from Oman to Liechtenstein.

Here is Why You Need An Adapter

The outlet and plug type used in Liechtenstein are C and J and in Oman is G. This is how they look like.

Oman

In Oman, outlets of type G are in use.

Type G

Liechtenstein

In Liechtenstein, outlets of type C and J are in use.

Type C

Type J