Well from a programming stand it’s likely limited to “Inventory” flagged objects. And most “creatures” in most games are not “Inventory” items. Although you could find the rare exception, like limited release winter event deployable snowmen. Or a “pocket doves” consumable for people who want to roleplay as street magicians. Translated to a “real” world, the magic of the bands likely understand the concept of an “Inventory” item, and what isn’t one.

Depending on the backend coding, there may not actually be a way to put a “creature” object into inventory. Even if you could somehow change a “creature” flag to an “inventory item” flag. Creating inventory systems for games can be handled many different ways. And can have disturbing mental pictures if you think about what happens as a “reality”. The Project Spark (a game for making games) had a default Inventory system that simply moved “Objects” out of the “World” bounding box and to a reserved location. The Objects’ Brains remained active. It allowed this to be done with any Object (everything that wasn’t the voxel terrain system). From apples to trolls and beyond, if it was an Object, you could program the inventory to “pick up, it.” However most games don’t do that, it can get very expensive (processing and storage/database) to do it that way.