PaperMC/paper-server/patches/sources/net/minecraft/world/item/EndCrystalItem.java.patch

--- a/net/minecraft/world/item/EndCrystalItem.java
+++ b/net/minecraft/world/item/EndCrystalItem.java
@@ -47,6 +47,11 @@
                         EndCrystal entityendercrystal = new EndCrystal(world, d0 + 0.5D, d1, d2 + 0.5D);
 
                         entityendercrystal.setShowBottom(false);
+                        // CraftBukkit start
+                        if (org.bukkit.craftbukkit.event.CraftEventFactory.callEntityPlaceEvent(context, entityendercrystal).isCancelled()) {
+                            return InteractionResult.FAIL;
+                        }
+                        // CraftBukkit end
                         world.addFreshEntity(entityendercrystal);
                         world.gameEvent((Entity) context.getPlayer(), (Holder) GameEvent.ENTITY_PLACE, blockposition1);
                         EndDragonFight enderdragonbattle = ((ServerLevel) world).getDragonFight();