First, lets make sure everyone is on the same page about what DExM is and is not. Merriam-Webster online (my preferred source) defines it as:
Main Entry: de•us ex ma•chi•na
Pronunciation: 'dA-&s-"eks-'mä-ki-n&, -'ma-, -"nä; -m&-'shE-n&
Function: noun
Etymology: New Latin, a god from a machine, translation of Greek theos ek mEchanEs
1 : a god introduced by means of a crane in ancient Greek and Roman drama to decide the final outcome
2 : a person or thing (as in fiction or drama) that appears or is introduced suddenly and unexpectedly and provides a contrived solution to an apparently insoluble difficulty
It is the second meaning that I am talking about. Basically, it is the "cavalry fatefully coming to the rescue." Lots of authors and writers use it as a technique to end a story, usually when the writer has allowed the plot or the characters to get into such a tough spot that a plausible reason for their victory or escape is not possible. The writer resorts to bringing in a more powerful and more capable entity to pull the characters' collective butts out of the fire. More than anything, Deus Ex Machina is spawned when a writer stubbornly refuses to lose a protagonist even when by all rights, the character should be dead.
It's a lazy technique. Basically, rather than working out a solution for the protagonists to develop on their own, the writer feels the need to just allow someone or something else to solve the problem. Yes, there are times characters get written into corners or improbable positions, but at that point I strongly feel the writer need to follow the story where it takes them rather than derailing it in a vain effort for a clean ending. I dig on tragedy. I don't like Deus Ex Machina.
The very same thing happens to the best of GMs. The desire for the use of DExM usually will come about for one of two reasons. First, Players are unpredictable beasts. Indeed, many players are fearless when it comes to their characters. A similar problem is capriciousness on the part of the players. In both cases the GM relies on internal logic or a PC's sense of self preservation for them to avoid certain dangers and unexpectedly the player charges head-long into certain doom. This can result in the GM feeling the need to pull the players out of danger and the only resource they have is to rely on an outside element to intervene. The use of DExM in this situation (to correct a GM mistake) is forgivable in my opinion.
The second occasion is a bit more of a problem and occurs when the GM simply has the plot centered on an enemy that the PCs are simply incapable of besting. These types of games are based around the idea of either ending in tragedy (like many Call of Cthulhu games and one-shots) or in arbitrary DExM. When playing in these types of inevitable DExM games I hated the feeling of my character needing another GM-darling come in and save our group from enemies we clearly were unable to confront. I vowed never to put my players in the same situation--they deserve more respect.
Let me give you a real life example of DExM. Years ago I was in a Vampire: the Masquerade game. The GM loved certain aspects of the backstory that simply were not for low-to-mid power level characters to tackle. Rather than simply avoid the use of those elements or introduce them through less powerful proxies, the GM felt compelled to force us into events where we served simply as spectators. I hated it. Often we would run afoul of these powerful NPCs and their world-wide conspiracies and we would dutifully wait for another ridiculously powerful NPC to come to our rescue. The GM thought he was doing us a favor by putting us into the middle of (what he thought was) a fascinating battle between NPCs whose mystery that was only exceeded by their power (2 points to whomever gets that movie reference). To us players the story was clockwork-like in its predictability and it was really, really frustrating to constantly have to look to NPCs to solve our problems.
Time to fess up. I have written a couple of RPG supplements, one of which is called Warrior Unbound for the game Tribe 8. Honestly, Warrior Unbound is not that great. I had some good ideas but fell into the trap of DExM while specifically trying to avoid it. In that story there is a specific part where a critical event occurs that has the PCs simply stand on the sidelines. I have read a couple reviews of that book that are spot-on in their unhappiness that the PCs are sidelined in what is, in effect, a poorly veiled DExM. I don't have a lot of regrets in general, but how I handled Warrior Unbound is one of them. I wish I had that time back so I could go back and erase any suggestions of DExM from that book.
So, how to deal with DExM? The easiest (and my least preferred way) is to use it as an escape button. Occasionally, players jump into events the GM is completely unprepared for and ultimately pay the price. Often this occurs because of player impetuousness as they push forward on campaign plots and twists the GM didn't anticipate. Things can spiral out of control as the GM feels obligated to present the obstacle or uber NPC as he envisions and the result is the players in over their head and possibly dead. This happens. Sometimes players pick fights the GM never thought they would pick or a story takes on a life of its own and the GM feels obligated to face the PCs with an insurmountable task. In these instances of GM mistakes or honest but bad evaluations of the situation by the players, it might occasionally be worth saving the PCs from certain death. Hopefully, the players learned their lesson and will not tread that particular plot thread again.
My problem with this technique is that it rings hollow to the GM and players alike. If they were supposed to die, they will be very aware that the GM had to step in arbitrarily and save them. Some players may be bewildered as to why they were saved or why they needed saving, and some players may even feel cheated out of a heroic death. My suggestion is that if you use this DExM technique, be up front with your players afterwards. Tell them why and how they got in over their heads and the use of DExM is a one time event. Don't fall into the habit of using DExM every time the players get in a nasty scrape ... once is enough. Otherwise, the players will consistently push the envelope and expect the GM to save them at the last minute.
Another way to use DExM that is significantly more elegant is to give the PCs control of the DExM element. If the players get to decide when and if the DExM step in, the arbitrariness and loss of control that normally come with DExM are mitigated. This technique also helps keep they players in control of their own destinies and will probably allow them to feel part of the DExM element rather than at its whim.
Take, for example, the simple use of a cellular telephone or flare. The PCs know that a highly capable SWAT team is mere minutes from jumping intot he situation and battering down the problem. Instead, the PCs are the ones trying to avoid the use of the SWAT team--to save lives, avoid property loss, or simply because it is more dramatic. The PCs could very well be facing an NPC or mob that they are incapable of overcoming- but the players don't know that, only the GM does. However, rather than having to ride to the rescue at the GM's whim, the DExM SWAT Team (who more than likely will have to solve the problem) are completely at the players' control. They decide when things are bad enough to require the SWAT team's aid. PCs may drop dead from the encounter, but it is because, in part, of the players actions. Leaving control over the player's characters is a good thing.
This technique does require some forethought on the part of the GM. If you see the players charging headlong into certain doom, intervene with another GM giving them the plot device that can call the DExM. Anticipate when things may derail and try to give your players the resources they may need to save their own necks. One thing to note: Players are infinitely creative creatures. Even those times you expect they will charge into certain doom, they often will pull something out that totally surprises you and possibly win the day despite your best expectations. Give the players credit and don't avert the showdown with the uber NPC altogether ... just give them a little insurance in the form of DExM.
Finally, my best situation for using DExM is to not use it. Accept PC death. Accept inevitable stompings. Accept tragedy. Great stories are born of these events. Only if the players really don't want to see the story end that way should DExM be an option--and then only as a one time favor. Tough love, baby. Tough love.
In Summary:
- DExM is born of the fear of killing off characters ... don't be afraid.
- End the story in tragedy if need be.
- Allow the PCs to time the use DExM--it gives them a nifty resource.
- If you absolutely have to, make it a one time event.
