Good idea, but a bit late? Removing the foundations allowed him to spawn and I got a bit stuck while climbing down (no hearts of the hero with me) but with my arrows from above and two on the ground we only had one death. After a bit of climbing practice in solo, I can get him alone without much problem, or be prepared with the hearts.
The only thrall we had remained passive and was of no help at all. Mine decided to remain on the perch and didn’t help at all which was odd because she originally ported to the ground, then back up to me.
All in all, a success, and due to your spawn blocking suggestion. Although, I thought the land claim to be limited horizontally, but not vertically, which would not have done the trick. I may test that lowering of the radius and see what happens.
Thanks, Ragnaguard. We actually built them around 12, pretty much directly across from the obelisk, two, actually, one to the sand, the other to the second floor. somewhere around there it landclaimed the dragon out of the spawnpoint. This was the base foundation to the second floor, the one to the sand was just to the right. So somewhere between this point and your instructions is the edge, which would actually be dependant on the land claim radius as Multigun mentioned.
Of course, they are no longer necessary since we now have the hearts of a hero and can remove the corruption when we are in the arena.