The use of portals or dimension or plane gates,as was the case with the wisping black tendrils durring the last bit,these uses are subject to damage incurred through a modifier roll,or can the simple act of being -in this case-evil,as Entropy etc have been,allow them to use them like the Githyanki,which in any case meamns they should get a wiser portal subjugater
-in the case of 20th level or so i guessed 2D20 damage for that type of portal
-also if the case is they were able to roll past them no damage,should the next rooms,or say the next green and dust infused tendrils gate have twice that damage for them getting away the first time,as such i am interested to know about these magi-doors