If the ender dragon hits an End Gateway portal, it teleports out. Eventually a new ender dragon will spawn and the battle continues as if nothing happened, its health bar doesn't even go away. But if you teleport through the End Gateway, you will find the old ender dragon there.
I waited next to the gateway and got the dragon to fly through three or more times, and when I went through the gateway I saw three ender dragons nearby immediately make a beeline for the main island. I followed them in flight mode (even sprinting I was slightly slower than the dragons) and when we got back to the main island apparently one or more dragons despawned at some point but I was left with two ender dragons.
Steps to reproduce:
1.) make a platform immediately behind the gateway with respect to the main island
2.) sit on the platform in survival mode until the dragon begins to charge at the player
3.) position the gateway between you and the dragon
4.) dragon enters gateway
5.) enter gateway and observe duplicate dragon
optional: follow dragon back to main island
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Comments 8
It works the same in an unmodified client. Proof in the second image.
I got the second image by summoning the dragon fresh after going to vanilla client, and performing the same steps as detailed in the OP. It works every time I try it.
MC-86836 describes that a dragon actually is able to enter an end gateway, but does not mention that the dragon is duplicated. As far as I can recall, when I reproduced that issue, the dragon was not duplicated either.
Are you playing in singleplayer or on a server? If you play on a server, is that server modded?
I have reproduce this on realms
Comment from MC-86836:
Confirmed in 1.12
Images:
https://snag.gy/zHhOpV.jpg (note the hitboxes)
https://snag.gy/KstVP5.jpg (enderdragons can go near the gateway portals if you stand on setups like this)
Edit: If you load a teleported enderdragon after you kill a dragon spawned because there is no nearby enderdragon, it will fly toward the main island and behave normally except without a heathbar.
https://snag.gy/PSlWZk.jpg
Edit: Also, duplicated dragons will not spawn portals
apparently one or more dragons despawned at some point but I was left with two ender dragons.
If two dragons are trying to perch on the portal at the same time, the second dragon may knock the first one off the island
Thank you for your report!
However, this issue is Invalid.
Your game, launcher or server is modified.
If you can reproduce the issue in a vanilla environment, please recreate the issue.
Any non-standard client/server/launcher build needs to be taken up with the appropriate team, not Mojang.
Any plugin issues need to be addressed to the creator of the plugin or resource pack.
If you have problems on large servers, such as The Hive and Hypixel, please contact them first as they run modified server software.
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