Abram fell sound asleep
This is an idiom. AT: "Abraham slept deeply" (See: rc://en/ta/man/translate/figs-idiom)
a deep and terrifying darkness
"an extreme darkness that terrified him"
"aliens" or "foreigners"
will be enslaved and oppressed
This can be stated in active form. AT: "the owners of that land will enslave your descendants and oppress them" (See: rc://en/ta/man/translate/figs-activepassive)