Strong barriers can be healed by placing charged cells in the corresponding strong cell tile, with higher tiers restoring a greater amount of Hitpoints. In case abyssal creatures break through the barrier, the remaining broken cell tile first has to be repaired with 10 guardian essence before a new barrier can be raised, starting from the weakest variant.
^Jagex. Mod Ash's Twitter account. 23 September 2023. Archived from the original on 24 September 2023. Mod Ash: "[would you happen to know the defense of the 4 barrier tiers for gotr? and if they have any other stats i guess] Looks like 20, 40, 50, 70 to me. I didn't see other stats beyond the HP that you'd have known about."