How to Upgrade the Vivarium - Hogwarts Legacy Guide
How to Upgrade the Vivarium

You first unlocked the Vivarium after completing The Elf, The Nab-Sack, and the Loom quest from Deek, unlocked by finishing The Caretaker's Lunar Lament and The Helm of Urtkot.
The initial Vivarium can only contain four distinct species at a time, but there are 13 Beasts you can find and rescue in the game—including the Hippogriffs, Thestrals, and the Phoenix.
There are three additional Vivarium upgrades you can add to the Room of Requirement, each adding four species slots for a total of 16:
- Coastal Vivarium
- Swamp Vivarium
- Grassland Vivarium
Note that all Vivariums can contain 12 active beasts simultaneously, bringing your total to 48.
Coastal Vivarium Upgrade

The first Vivarium upgrade will automatically be unlocked after you've collected ten beasts and started The Plight of the House-Elf side quest. At this point, you should've done The High Keep main quest, so you've likely collected the required amount of beasts by the time Deek's questline is available.
Swamp Vivarium Upgrade

After completing The Plight of the House-Elf and the Fire and Vice main quest, you'll get an Owl Post from Professor Weasley, who informs you that Deek can teach you how to breed beasts—this will unlock the Foal of Dead side quest.
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