> And still they are not aware what powers **lie** between their hands!


Powers are plural. The third person plural ('they') of the verb 'to lie' is **lie**.

Past tense would be lay

> And still they were not aware what powers **lay** between their hands!

Present:  
Singular: I lie, you lie, he/she/it lies  
Plural: We lie, you lie, they lie

Past tense is all 'lay'.