Learn Russian: Секретарь всегда владеет важной информацией. - The secretary always possesses important information.

The verb владеть (to possess, to have at one's disposal) is one of the special verbs that require their object to be in the Instrumental case. Verbs related to control, management, or possession (like руководить - to lead, or управлять - to manage) frequently follow this pattern instead of taking a standard Accusative direct object.

Could I use the verb иметь (to have) here instead of владеть?

Yes, you could say Секретарь всегда имеет важную информацию, but notice that иметь takes the standard Accusative case. Using владеть is often preferred in professional contexts because it implies "commanding" or "having mastery over" the information, rather than just passively having it.

How are the Instrumental endings formed for the phrase важная информация?

For the feminine noun информация (which ends in -ия), the ending changes to -ией in the Instrumental case, making it информацией. For the feminine adjective важная, the standard Instrumental ending is -ой, making it важной.

I've seen feminine nouns ending in -ью in the Instrumental case. Why doesn't информация end that way?