حَتَّىٰٓ إِذَا فَتَحْنَا عَلَيْهِم بَابًا ذَا عَذَابٍ شَدِيدٍ إِذَا هُمْ فِيهِ مُبْلِسُونَ
Hattaaa izaa fatahnaa 'alaihim baaban zaa 'azaabin shadeedin izaa hum feehi mublisoon
until We open a gate to severe torment for them- then they will be plunged into utter despair.
Until, when we opened upon them a gate of severe punishment, they were plunged into despair.