The Cloister attacks people only when people try to leave it, but it was unable to stop TARDIS from leaving. Maybe, the Dalek which was trapped there didn't have emergency temporal shift tech during the Cloister War, but TARDIS is a common thing among Time Lords.
Then, why were Time Lords afraid of Cloister? We can see the emphasis on keeping out of the perimeter. Also, The Doctor ran into the Cloister because Time Lords couldn't pursue him there. The queen (or, whatever) of the Sisterhood of Karn also concluded this easily. Why couldn't Time Lords pursue The Doctor into the Cloister using TARDIS?