His Most Excellent Majesty Xen Huong, Celestial Dragon Emperor of the Imperial Palace of Grand Cathay is the most important man in the entire history of the ogres, for it was him that caused the destruction of the ogre homeland, introducing them to their cruel god and beginning their diaspora.
Bored of the constant raids on Cathay the Emperor asked his astromancers to assemble to call down retribution upon the ogres. Soon after a meteor struck the heart of the ogre nations, but this was no normal impact. The comet drove itself through the entire world creating 2 great maws, complete with rows of serrated teeth.
The impact was so great that it killed the majority of the ogres and turned their fertile land into a harsh desert, whipped by winds laced with warpstone dust that left the entire land uninhabitable.
The surviving ogres fought for the last remnants of food, and when that was gone fell to cannibalism as the only source of sustenance... but something was wrong, no matter how much they ate no ogre could quieten the gnawing hunger within them. The last surviving ogres were forced westward in a desperate search for food, which would never be enough to feed their eternal hunger, which the ogres linked to the giant crater/hole left by the meteor, which they gave the name the Great Maw, and worship as a god.
As they travelled westward the ogres found themselves trespassing in the lands of the Sky Titans: immensely powerful beings that united would have easily crushed the fledgling ogre kingdoms, but isolated in their mountaintop castles they were all eventually brought low (and eaten) by the hungry ogres.
The ogres now have a relatively stable culture within the Mountains of Mourn with the strongest ogres taking control of their tribes (by defeating and eating the previous Tyrant in a duel). Ogres are constantly looking for food; some tribe rely on hunters bringing prey back from the mountains but most fill their need by contact with other races. The more noble ogres receive food as payment for fighting for other 'lesser' races or for guarding their caravan routes through the mountains, while more malign ogres raid for what they want (or receive tithes to prevent them raiding, which often acts solely as an aperitif for the ogres, who then raid anyway).
Whatever happens you can't trust an ogre beyond their next meal: so long as you keep feeding them they'll be your friends... but step between an ogre and his next meal and you'll likely become it.
Ogres have one of the best selection of models around for character and modelling potential.
Building the standard kits without conversion will give a pretty good looking army, every unit has a character all of its own and gnoblars/maneaters are just about the most characterful units in the entire game. With that said a little conversion skill will turn a good looking army into a impressive looking individualised army: the larger scale to the ogres means they are an ideal place to learn modelling skills that can then be put to good use on more fiddly models.
Ogres move faster and hit harder faster then pretty much any other army around and are backed up by superb shooting in the form of leadbelchers and better artillery... all of which can mush most enemies in combat. Sounds too good to be true? Well yes, there are some downsides too: ogres tend to have poor leadership and while they have 3W each they tend to have fairly poor armour saves and won't have enough models on the table to sustain a war of attrition for long.
Ogres are the glass hammers of the WFB world: they do a lot of damage, but can't really take much in return.
The game is split up into 4 phases: movement, magic, shooting and combat... here's a quick runthrough of how ogres fiar in each.
Movement- ogres are the fastest non-cavalry army around and with gorgers able to appear behind the enemy and yhetees able to cross any sort of terrain an ogre army can normally outmanouver pretty much anyone, letting you fight the battles you want to fight, while being able to avoid the fights you think you'll lose.
Magic- The Lore of the Great Maw is the principle lore of the ogres and it has some of the best augment spells in the game, helping ogres to survive enemy attacks and then making their own nastier in return. The only spell that isn't really all that helpful is the 'best' spell in the lore: simply called "The Maw", which is an almost perfect anti-ogre weapon, and since a misfire will lead to the enemy placing its effects choosing to cast this spell is at best the roll of a gambler, but at worst the last act of a desperate player.
Shooting- Leadbelchers are second only to flamers of Tzeentch for sheer offensive power, but while flamers might be able to march and shoot (and stand and shoot the ogres back their cannons up with being ogres, meaning they are still lethal in combat. Backing these guys up are the artillery, either in the form of a gnoblar jerry-rigged catapult or ransacked sky-titan cannon both of which are mounted on powerful chariots pulled by bad-tempered rhinoxen. While they don't have the power to rival a dwarf or empire gunline ogres can certainly bring enough pain to make most armies wince.
Combat- Ogres might move fast, but they hit slow. low initiative means they mostly strike last, but when they hit they hit hard. Ogres by themselves are a challenge for most enemy units, but add in characters and magical augments and they soon become some of the strongest units in the game: their lack of armour means you have to use them tactically, but get it right and whole enemy units will just evaporate from your path.
Lords and Heroes
Tyrants are leaders of a tribe of ogres, a place they've won by being the biggest and strongest of their kin. On the table, and properly equipped, these guys are the equal of pretty much any other single model in the game (be it lord or monster).
Slaughtermasters are the chief cooks of a tribe, and when your worship revolves around eating you know you have to respect the cook. A slaughtermaster is nearly as powerful as a tyrant but can also buff whole ogre armies with his magic: a common site in any ogre force the slaughtermaster should never be underrated.
Bruisers are often kin of the tyrant, but they don't retain their rank through nepotism: they are second only in strength to the tyrant (or each other). Normally seen carrying the tyrant's battle standard bruisers are some of the nastiest heros in the game, often capable of taking on and beating lord level characters.
Butchers are every ogres best friend, but they are very careful to avoid showing favoritism to anyone other then the tyrant (lest they get eaten). A somewhat rare sight in 8th where slaughtermasters out class them somewhat but sometimes taken to give the ogre player access to the lores of beasts, heavens or death.
Firebellies- devotees of the Volcano God (!!) these ogres must consume liquid hot magma to show their readiness to serve. Giving access to the Lore of Fire and bringing a S4 breath weapon means that ogre players that focus more on pure offense tend to employ a firebelly for their magic.
Hunters are loners, which is probably a good thing because their rules stink. They do give you some nice options and look and feel fairly cool, but they just don't do enough to justify even half their points...
Bulls (ogres) are the ogre equivalent of a civillian: they aren't big, they aren't clever, but they do eat lots and hit hard. Throw some of these guys into a unit and direct them at an enemy and there is bound to be blood flowing. A solid choice but nothing remarkable.
Ironguts- the 'guards' of the tribe. Normally seen as retinues for either the Tyrant or high ranking Bruisers. Ironguts have great weapons, giving them a little more offensive power but their main advantage in game is that they can have a magical banner,
Gnoblars- almost useless unless you need a tarpit, but with Ld5 I hope you have a general and possibly a BSB close by to keep them in the fight. The trappers upgrade is interesting but isn't going to do enough to really make the gnoblars worth taking.
Leadbelchers are awesome. Anything within 24" of them is going to be feeling their sting, but get into combat and you'll be no safer. A solid choice of support unit.
Yhetees- a distant kin of the ogres, fast moving over any terrain with magical ice weapons that can kill even ethereal enemies... but unless you fight a lot of etherals I just wouldn't bother with them.
Mournfang- shock and awe personified. If they make it to the enemy then they'll likely kill their way through in fairly short order... but that's the only 'order' linked to these guys: with fairly crap Ld and low model count they'll often run away as soon as they take a casualty.
Maneaters- they've travelled the world and have learnt skills that can greatly aid your army... if you can afford their price. High points cost with no additional protection over standard ogres sees these guys rarely used... but the ability to pick special rules for them can make them exactly what your army needs: poisonous sniper weapons killing enemy characters or swiftstriding scouts appearing behind the enemy ready for early-game massacres are 2 of the best combos.
Ironblasters- its a S5 chariot with a cannon on the back which not only fires mutiple cannonballs (roll 2 bounce distances and take furthest) but also has S10 grapeshot. Very very nasty unit...
Gorgers- deformed ogres, abandoned to the black pits of the caves under the ogres' mountains. Almost totally devoid of thought they are lured to battle by the scent of blood, appearing from any table edge and being totally unbreakeble makes them a huge threat to rearguards and warmachines.
Slavegiants- rubbish, forget they exist.
Scraplaunchers- move and fire artilery just like ironblasters but instead of a cannon they pack a S3 large blast stonethrower with killing blow. Capable of tearing the hert out of large infantry units the scraplauncher is also the funniest and most characterful of any ogre unit.
Ogres are the cheapest army around (only rivalled by WoC), with both the battalion and bull boxes being great value for money (a phrase rarely directed at GW products). Even better is that ogres come with a great vaiety of little add ons and base scenery which can make units look great but are also great helps for converting other models. That really is the word for money saving with ogres: converting. It is the character models that really start to ratchet up the price for buying an ogre army, and with such little choice available (just 1 tyrant/bruiser, 1 slaughtermaster/butcher and 1 hunter) converting bulls/ironguts into either characters or maneaters is natural both to save money and to give your army more variation.
Ogres are a cheap army to start and are quick to paint and with such excellent value for money on their basic sets that if you can convert your own characters/elites you'll save a bundle. On the tabletop ogres can now compete with almost anything but still have a remarkable vulnerability to initiative based magic. Generally if you can get stuck into the enemy before they can kill significant numbers of your ogres you'll bash your way straight through.