An adventurer is being swallowed whole by a Tyrannosaurus; Things look bleak. Suddenly, the player has a brilliant idea! They crack open a Feather Token: Tree inside the dinosaur's mouth. The description for the item tells us the size of the tree, and that it springs into being "instantaneously". Sadly, such questions as "can the tree grow inside an enemy's stomach?" and "how much damage does that do" are left to the imagination.
Are there rules anywhere that cover this situation? Official sources are preferred, but a 3rd party source, or even a well written blog post is sure better that what I have now, which is nothing.
Best Answer
Unless you can throw a tree, you cannot throw a feather token and make it turn into a tree on your target. Because activating a feather token is a Standard Action. Just getting this out of the way as people try this more often than not.
Now, if you are inside a creature, and manage to activate a magic item, it will work normally. If you are Swallowed you are also grappled, which states that you can take any action that doesn't require both hands. As long as you don't need both hands to activate a magic item, you will be fine, you are not restricted from your other actions.
If you look at this topic, Sean K. Reynolds said:
So, he can activate any magic item, shuffle through his bags and pockets, draw or shealthe weapons, drink potions, cast spells with a concentration check, try to escape the swallowed condition by succeeding a grapple check and go back to the creature's mouth, etc.
However, if you look at the magic item stat block, you will see that the feather token uses a conjuraiton (creation) spell, Major Creation, which say in the CRB:
That said, in the case of the Tree Feather Token, it cannot be activated inside another creature.
In my table, i would allow the item to be used, because of the Rule of Fun of describing the scene to my players.