Beckon druk'trar works in underground areas, similar to 'manifest shadow' spell. But 'forsaken portal' won't open: 'The accursed daylight prevents the opening of such a portal', though there are obviously no daylight in the area. Maybe, if it is by design, change the echo to something like 'Forsaken portal may be opened only at nights'?

A forsaken portal requires a strong tie to our plane, which is strongest at night time - not JUST in darkness.

Echo changed to reflect that.