Terrarium

The Terrarium is an item used to make Cages for Critters caught with the Bug Net or the Golden Bug Net.

Cages cannot be opened, broken, or un-crafted, so once a critter is crafted into a cage with the Terrarium, that particular Critter can no longer be released.

Trivia

 * Gold Critters have a unique sprite with golden lids and bottoms.
 * Terraria is the plural of Terrarium.
 * The Terragrim, Terrarium, and Terraspark Boots are the only Pre-Hardmode items with 'Terra' in their names.

History
Terrarium