In the film we see that the Gamemakers can summon trees, some sort of hounds, fireballs, etc. How does this work? Can they summon anything they want? Are there any restrictions, limitations or rules?
Certain items are already in the Arena as specific objects to be made use of or obstacles to overcome as part of the design for the Arena; since each Arena is designed many years before and the creation of such takes some years.
However there are certain items that are introduced to keep the games "exciting" and whilst you would expect that there are a few of these such as the fireballs that are preplanned, there must be a small arsenal of different weapons of effects that can be called upon at the whim of the Gamemakers.
As to limitations or rules, the only limitations that I can come up with are those that keep the games interesting such as:
- Don't over attack the players (i.e. don't kill them all at once)
- Allow the players who escape time to recuperate
- Don't interfere in existing combat
Other than that there are no rules, anything goes.