Storm of Magic
Storm of Magic is an expansion for 8th edition Warhammer Fantasy Battle, with a big(ger) focus on magic.
Once upon a time, GW was sad. Though they had found a way to make people buy more shit for 40k (namely Apocalypse), the sales for Warhammer Fantasy Battles was kinda lacking. So they sat around a table and began to think how they could remedy this and gain more money. Doing the same that happened to Apocalypse was not an option: larger scale battles of WFB could easily take your entire table, and making them even bigger would only bog down the game. Vehicles were, aside from the Empire and Dwarfs, not an option either. So, they took the only thing that remained: monsters. But an expansion based solely on monsters was a bit bare-bones, so they took another central part of WFB: magic. Based around monsters and magic (sounds like a D&D clone), they created Storm of Magic.
The world of WFB is rather fucked: there's a large hole at the north pole of the world, called the Realm of Chaos, where Chaos pours into the world. This gap in the world also created magic: wizardry is for the most part the purification of the winds of magic so it can be used for a noble purpose. Magic is affected by strong fluxes; the power of the winds of magic can wax and wane in a matter of minutes. When the magic in the world is very strong, this can result in a storm of magic. Ancient effigies sprout from the land, monsters are drawn to these places, and ancient artefacts surface. When such a storm takes place, the people of the world marshall their armies and go to these places, for he who controls magic controls the world. This tends to lead to massive and brutal battles, armies supported by their wizards wielding power unlike they ever had before.
Storm of Chaos can be divided into four parts: magic, monsters, armies and artefacts.
There are two main differences gameplay wise from the regular game: Since magic is strong during a storm of magic, you gain 4d6 dice for the winds of magic, and you have a doubled pool for total magic dice. Also, you gain 25% of your army's points to spend on monsters, pacts and artefacts (so you get 500 points for a 2k army, 750 for a 3k and so on)
Magic works the same way as in the basic rulebook, with a few additions.
The first is the Wheel of Magic, built into the back of the book. It is a wheel divided into eight parts, once for each of the winds of magic. At the beginning of your magic phase you spin the needle: the part that it ends on is Ascendant; giving a notable bonus (+5 for battle magic, +3 for Dark/High magic, and +4 for the rest). If you control at least one Arcane Fulcrum, you can roll a D3 and turn the needle that many spaces (exactly, not less), to gain an edge on your opponent.
Storm of Magic always starts with four Arcane Fulcrums on the battlefield: special buildings usable only by wizards to boost their power. Taking control of these gives your wizard access to nifty defenses, bonuses for your army, and most importantly, allow you to fuck up your opponent's army. There are three stages of power: Presences, Equilibrium, and Dominance, reached by controlling a Fulcrum, controlling at least as many fulcrums as your opponent, and controlling more fulcrums than your opponent. Some lores of magic gain a spell for each of these stages, and some only one.
Most of these spells are powerful game-changers, like the addition of no less than eleven new iterations for the Purple Sun of Prepare Your Anus, an insanely powerful augment spell for the Tomb Kings, the ability for Damsels to turn EVERY (including yours) character on the battlefield into a toad, gimping their stats (use this on a Bloodthirster and kill it with archers for epic lulz), Khorne throwing a brass skull at the caster of any of the other gods if they miscast, and a truly epic spell usable only by Slann Mage-Priests that forces your opponent to remove a number of characters and units if their number surpasses yours. Also the probably most powerful spell reduces every stat with the exception of S,T,W,A to 1 (yes LD 1 for your whole army) for every enemy unit on the field oh and every enemy mage can't cast, when they are subjected to this spell and it stays in game, so the enemy has to ban it by a nice 25+. This turns every enemy unit which doesn't have S=T=10 into absolute crap. I encourage /tg/ to try and break the hell out of this.
There are a few other spells that all wizards get, like teleportation between Fulcrums, a Mind War-esque effect, and a spell that allows you to summon up to 300 points worth of units out of nowhere to fight at your side. These give no victory points to your enemies, so make good use of this spell, like having three cannons appear the fuck out of nowhere, or have a Daemon Prince elbow-drop onto your enemy's wizards. Units summoned this way are very vulnerable to the Lore of Light, so be careful if you use them.
One of the biggest selling points for Storm of Chaos is that you can summon monsters. These monsters range from well-known, generic critters, to creatures that regularly appear in only a single army book, to completely new beasties. Many of these can also serve as mounts. Some of the more notable are the Bonegrinder Giant, which are Giants on steroids; the Cygor, a Beastmen native which will fuck up casters and anyone carrying a magic item of any kind; Chaos War Mammoths, which are combinations of giants and SEVERAL CRATES OF FUCK YOU; Exalted Greater Daemons, which are the bigger brothers of regular Greater Daemons (and cost 775 points each); Dragons, which come in several colors (specifically Red, Black, White, Green and Blue) and sizes, with the largest capable of being wizards (if you make them, please report to your local Commissar for re-education); a number of critters from the Ogre Kingdomws army book; the Great Taurus and Lammasu, which herald the glorious return of the Chaos Dwarfs (at least via Forge World); the casters and Fenbeast from the Albion stuff back in 5th edition; oh, and FUCK YEAH ZOATS!
Now, on paper they don't sound too bad. Unfortunately, they are. Every caster on the battlefield knows a spell called Unbind Monster, a 3+ cakewalk that has a good chance to either remove the monster, make it go berserk, derp out, or make it useless in another way. So you really shouldn't bother with monsters all too much, which is a shame, because they look awesome.
Another Opinion: The Above Mentioned Spell, Unbind Monster, can be a deal breaker, however a further D6 must be rolled.
On a 1: Nothing Happens 2. He gets roid rage with a frenzy that can never go away. 3. Gets Derpy and suffers Stupidity. 4. Still Fights For you but doesn't get the Battle Standard Bearer's or General's perks. 5. The Monster goes home, leaving the battle as a casualty. 6. Monster hates everything and wants a piece of everyone, friend or foe.
While the spell has its perks, it only has half a chance of doing anything major, and while it is super easy to dcast it is also super easy to dispel (chances are both sides have tooled up wizards to work with).
In a game of storm of magic, you can have a single pact with a being and its servants: either a Daemon, a vampire or a Tomb King. This allows you to field more units that either complement your army, or just size it up if you happen to play one of these armies. Unlike other ways to increase your army size, there are no special ways for your opponent to destroy these units.
Instead, you have to roll for Fragile Alliance every turn: if you fail a third time the entire pact army disappears. The summoned armies have their uses, but don't count on them as replacements for your own units.
The final part of the book are artefacts, powerful magic items that can change the battlefield and give powerful bonuses. You can only have one of these items in your army (two in a Grand Army), but do not follow the rules for the normal allowance of carrying magic items (they start at at least 100 points, and can be given to any character you field). Some can summon forests that beat the shit out of anyone that enters them, another turns its user into a giant, two create buildings, and another that gives massive bonuses to the bearer and its unit.
Some of these items are rather useless though: there's one that forces a character to cast a spell from either the lore of Shadows and Death that has an additional cost of anywhere in between d3 to 3d6 wounds to the caster's unit, possibly including the bearer (Take in a vampire counts army on Heinrich Kemmler, and put him in a massive brick of zombies. Then, apply end times magic rules. Watch as your opponent weeps before your RETARDED magic phase.), or the weapon that allows you to fuck shit up in challenges, but it automatically and unavoidably kills its bearer at the end of the challenge, switching to another random character on either side.
Storm of Magic is for those players who want to fuck up the enemy with even more magic than normal WFB already has. Its concept is nice, but somewhat poor in execution, with monsters being near-useless, only a few usable artefacts, magic being grossly overpowered and pact armies being undependable at best. You could check it out for lulz, but it's not a big replacement for the regular game.
It's probably worth noting that the rules are explicitly written so that you can choose to use some of them and not others; thus, if you wanted, you could just use the Scrolls of Binding and play normal games with EXTRA MONSTERS.
Incidentally, Storm of Magic was written by two people. Jeremy Vetock, who you might remember from Warhammer Armies: Skaven (and more recently the writer of the Tau and Dark Angels codices). The other, well, guess. Guess who. Guess. The fuck. Who.