"... the horses go through the portal but you will not ..."
Can someone please explain why this is? Just curious.
Allow me to attempt at an explanation, even though I am nowhere near an expert on all this.
The main cause why the end portal won't work is a Bukkit plugin changing how worlds are linked, like how we have wilderness and nether, but also perpetual end. Stepping on a "legit" wilderness end portal in a discovered fortress is just like stepping through air with a pretty effect that you can't see through.
With a little experimentation, we found that items will travel through it, to our own end world. And that experimentation continued to entities such as cows, villagers, etc. So, you have to move the horses into the legit wilderness end portal in order to move them into our end world, and then move them to the dragon's grave portal to our main world.
A bit more of info: we also thought we had to have another player in the end, to receive the horses being brought through, to kind of guide them, and mainly keep them from falling off into nothingness. However, it seems we may not need another person, I figure it's better to be safe than sorry. Same goes from the end to the main world.
Hope this clears things up
Also big thanks all of you, I love doing everything I can to help out!