×release the spider, kill the brain, use the spider as an obstacle to divert the goblin's path.

×But the spider follows too closely and traps me when I go for the brain...

×
if spider is at 1(with one square between you and spider, obviously) when you are ready to kill the brain, the spider won't trap ya.

×One square of distance is enough. You should be able to get that by circling around the spider and using your sword as an obstacle.



With one square of distance, you can get Beethro at 1 and the spider at 2. When you go southeast from 1, with sword already in the right direction, you kill the brain and so the spider will use unbrained movement, staying where it is.

×if you broke the crumble walls in upper sector, that will be a possible place to park spider.
Step on (14,11), then go north. Park spider at (13,5)

This will give you distance. Now you may park spider at (14,22) as you go to push Goblin .