All fiction writers play God all the time, and fantasy writers more than anybody. That's what writing fiction is - creating your own private little world to play in, complete with people, places, good, evil and all the rest of it.

Fantasy writers make the rules, and no other genre offers its writers such freedom for creativity and expression. You draw your reader into a world never seen before; a world entirely of your creation and based on your imagination. Perhaps the setting is a flat plate, with the same landscape, plants and scenery as our own Earth. Alternately the world could be made of ice, but not necessarily cold ice! Maybe your characters enact your story during night time, when the moon (or moons) are high in the sky. Daytime is for resting, because that’s when the sunlight used to energise the world is stored. It can also damage your characters in some way – burning or blistering the skin or causing them to fall into a deep coma should there be any exposure to the sun’s fierce rays. Or perhaps the sun has no warmth, and anyone caught in its light risks being frozen into a block of ice… a most uncomfortable event that can be treated, but each treatment takes a few years off your life.

However, while this might seem like a magnificent freedom for the author, it isn't really. If anything, it's a nuisance, a disadvantage - because it means you have to explain the rules to the reader as you go along, without any boring lectures, and you have to do it fairly.

The biggest risk a fantasy writer faces is losing credibility. It’s all very well to create a fantasy world filled with interesting and diverse creatures and characters, each of whom has some special gift/talent. In fantasy a reader knows only what he’s told, so while a talking cow is perfectly acceptable and believable, a talking cow that flies a space craft or wields a sword is not. That doesn’t mean you can’t create a character that is a variation on a talking cow. Just give it another name – instead of cow make it something obscure, like a zenndrah. Then paint a description of the zenndrah, making it part of the detail in the story. Mention the fine, curved horns silhouetted in the forest, his fine, pearly flank shimmering in the moon’s light. Describe his significant footprints in the sand of the banks of the river, with one long, extended centre toe with a thick sharp nail between to smaller, nail-less digits. His bellow can sound a long, mournful greeting as he approaches a character. If you want him to captain his space ship he could carry a helmet and goggles. Want him to use a weapon? Make him hand a character a book, or perhaps draw a diagram in the sand while talking to the hero. After doing this his skill in swordplay will be obvious to your reader.

Fantasy readers must never feel betrayed or tricked by a writer. Let me create a scenario for you: the Evil Emperor has laid waste to our hero’s army and pierces our hero through the heart. Instead of succumbing to his dreadful wound, said hero stands up, seizes the sword and slays the Evil Emperor with the weapon. Any reader will be horrified at this development, unless you’ve told him/her earlier in the story that your hero has been gifted a suit of enchanted armour imperious to that specific sword, because the armour and the sword are supposed to be worn by one person – the king. They were parted when the Evil Emperor killed the hero’s father just before said hero’s birth. Evil Emperor thought the one who held the sword would be The Ruler of the World – he didn’t realise the armour and the sword must be used by the same person, and that person was the rightful king.

You play God when you create the world and the story set in it, and once that's done, you do not intervene directly. You don't change the rules in the middle of the game. You don't let the detective summon the victim's ghost and ask whodunnit in a mystery, and you don't change the laws of magic midway through a fantasy. You don't spring surprises on the reader. If you're going to use some loophole in your invented rules, then you need to let the reader know as soon as possible that that loophole exists, and you want to try very hard to not make it look like that loophole was created just to make your plot work.

Here are several situations to avoid at all costs:

Don’t let the hero win the main battle with the Evil Emperor because he’s younger and fitter. The Evil Emperor is in this position because he is clever, strong and powerful. Have your hero’s mentor teach him of a flaw in the Evil Emperor’s technique, or a weakness from his past that can be used to make him drop his guard, thus giving our hero a chance of defeating him.

Don’t set up a classic battle between good and evil, and then have a god or similar being fly down from a cloud/mountain and kill the bad guys. What is the point of setting up a wonderful world filled with incredible, exotic creatures and then spoiling the climactic battle in this way?

The zenndrah shouldn’t just run an evil character through because he’s sworn to protect the hero – he can do it because the hero’s lover taught the zenndrah a few sword fighting skills so that he would be able to protect the man she loves should the occasion ever rise.

Don’t let the hero survive a lightning bolt because his family is immune to lightning. Rather give him an encounter earlier in the story with a character who hands him a talisman to protect him from lightning bolts. Or write a chapter prior to the last battle where our hero attends a sacred ritual that makes him immune to lightning bolts.

Never create a miracle to get a character out of a difficult situation. Certainly a corpse might get to its feet and attack the creature that took its life, but don’t make it get up just for the sake of getting up. The hero might utter a spell that brings the corpse to life for a short time, or perhaps the weapon that was used has to be used twice to ensure the corpse does not get up again.

You play God at the Creation, and then you sit back and watch it all unfold. If you've done it right, you won't need to show your hand again.