Structures
Origin Island, the Hunters' Campsite, the Graveyard, the Summoner's Lab and the Archmage's Settlement.
Origin Island
A long lost island found in the vast oceans, holding the secrets of familiars' existence. Its only inhabitants are little lost souls, very early forms of the familiars that never reached their final form. These creatures can be bottled using empty bottles, and then used in rituals.
The island's center holds the ritual site: a Ritual Core surrounded by four familiar statues. See Rituals to learn how to use it.
The island's suspicious sand can be brushed for treasure: several familiar trinkets (Blessed Calyx, Chain of the Hunter, Golden Bell, Emblem of Electricity, Contaminated Cheese, Conjurer's Candlestick and Forgotten Crown), the Holy Water Grail, the Statue of Willpower, the Cracked Hourglass, the Tiny Shield and the Familiar Idol. Its chests hold brewing, research, fishing and workshop loot.
To locate this island, you first need a Sniffer, which sometimes finds Crystal Berries. These berries can be fed to your tamed familiars, which makes them vaguely remember their past and how they were born, condensing into Memory Fragments. Memory Fragments can be used the same way as Ender Eyes to locate the Origin Island.

Hunters' Campsite
Hunters live in groups, so they built campsites along their main hunting spots, mainly forests where plenty of prey wanders around. These campsites can also be found with a Furled Map from the Origin Island's cartography chests. Their chests may hold the Chain of the Hunter.
Graveyard
This structure belongs to the Soul Sand Valleys, a place where death rules. Necromancers are naturally attracted to these places, so you will surely find them here. Its chests may hold the Insignia of the Lich.
Summoner's Lab
Summoners' curiosity towards sculk made them stay in Ancient Cities for a very long time, so they built their own laboratory in the city to make better use of their study time. Its chests may hold the Forgotten Crown.
Archmage's Settlement
Archmages travelled to the End to study the secrets of the infinite void, so they needed a place to stay in the meantime. They built temporary homes all around the End, where they can study and make discoveries. Their treasure chests may hold the Shiny Crown and the Heart of Ender.
