The dragon
The dragon has 320 health. No single hit can take more than six per cent of that, so a burst combo will not delete the fight. Explosion damage against it is cut to a quarter. It perches for at most six seconds. It calls in help at three quarters, half and a quarter health.
What is out past the ring
Vanilla end cities are off. In their place there are ground level remains of ancient cities, built in purpur, and among them barrows. A barrow holds either wings, or shulkers, or a trap.
Barrows are the only source of elytra in the world. About one in three holds a pair of wings. About one in three holds two shulkers. The rest are traps.
Shulkers repopulate the remains, so shells renew, and they renew only out there. You cannot build a shell farm behind a town wall.
Endermen in the pillar ring attack on sight.
It grows back
Sculk grows back. You cannot clear the End permanently, so no corridor you cut stays a safe walk for ever. Respawning the dragon does not wreck what has been built.