"A not so simple way to return to the Overworld."
While traveling around the world of the End, you can come across ancient ruins.
There is a destroyed (or not) frame of Runed Flavolite and six pedestals around it.
These are the remains of the majestic portals that once linked the worlds of the End and Overworld.
To activate the portal you need to recover frame (if it's broken).
And place 6 Eternal Crystals to pedestals.
After you'll place the last crystal, portal will be activated.
Runed Flavolite (to recover the frame) and Eternal Crystals can be obtained by Infusion Rilual.