So, in my story, there are six main categories of magical abilities, and everyone's able to have 5 abilities at a time. Each category of power has its own limitations on, and rules for, their use, and one category, called "Tribute", allows you to temporarily disable a certain number of your other powers to manifest something into the world: either an object, a totem that alters physics in the area around it, or a loyal animal companion. These will persist until they are either dismissed by their creator or destroyed, and either way the tribute power and the powers tributed to make the creation will remain unusable for an hour after the creation's destruction or dismissal.
Now I like this concept, but a problem with it stuck out at me almost immediately:
Nobody would want to have them.
No warrior with any significant backing or funding would disable any of their own powers in exchange for a cool magic sword if they could have their squire conjure it for them, or pay a civilian to borrow theirs, and still have all of their own powers intact. And the same goes for familiars: just have somebody who'll be far away from danger summon their own and then instruct it to follow someone else's orders. Boom, same benefit, but without anyone who'll actually get into a fight paying the price to their power.
While obviously for people and organizations with limited resources or manpower this wouldn't be an option, it still seems to me that it'd be pretty lame to have an entire category of cool powers that would never see personal use in "high level play", as it were, because whenever you have the option it's always better for someone else to use them for you. So naturally the obvious course of action was to contrive mechanisms to make this sort of abuse impossible.
For items, I figured that since all tribute powers are all manifestations of the user's spirit animal / familiar, they have a mind of their own and, upon recognizing an attempt by somebody other than their master to use them, they instantly teleport back to their master's side.
The world-altering totems aren't a problem because they're stationary and are generally intended to be used by more than just their creator.
But for summoned beasts? I can't think of anything to prevent the "I want you to do what this guy says" exploit that wouldn't involve making them amazingly unhelpful to people working with a group, or creepily sociopathic towards anyone who isn't their master (the main character has one of these and I want him to be an endearing and likable animal companion for him).
Why would using somebody else's summoned familiar, ordered to obey you, not work, or at least not work well enough to keep people from making the sacrifice to their powerset to use their own?