Description of feature
an very expensive block/item that when used before summoning the wither storm,
will restrict the wither storm's movement within a very large area
(become a wither storm impact zone, but players are safe to develop far outside the zone)

this barrier only limit the movement,
so attacks are still far-reaching and hit beyond the barrier (no cheesing by staying outside the barrier)
players still have to go within attack range to challenge the wither storm.

when viewed sideway:
safe zone | attack range | movement range | attack range | safe zone

so instead of unrestricted destruction
players who are new or want peace, can still develop very far away from the center, without fearing the destruction
and anyone who is willing to challenge, can gather around it

maybe make it optional in configs too,
because it kind of nerfs the storm,
but will make it easier to add to servers.

Probably should be a creative-only or post-storm thing, but it would still be cool.

if it's obtainable in survival a cool advancement for using one could be 'YOU SHALL NOT PASS!' or something

what about one that does the opposite (movement range | attack range | safe zone | attack range | movement range)? perhaps it could be only obtainable after killing the storm the first time, since it would be useful but a bit overpowered for the first run.