Would love to!

it's one of my favourites:
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First off, I'll say that the Lore of the Great Maw has a great synergy with the Ogre Kingdoms army. Lots of buffs for combat in the list as well as a brilliant regeneration granting spell. These spells can also be upgraded to affect all units nearby, so it's good to have your wizards up close and personal.
Taking into account most of the OK's troops are movement 6, you can make the most of these very quickly.
Which leads me to the first bit: Bloodgruel Lore Attribute.
Ogre Kingdom wizards are in the rare group where they can take armour (have ironfist on their equipment list) and their stats are not bad. Stick them with a good weapon and armour and you've already got a fair decent fighter.
Add to this the fact that they can buff all units around them and it starts to become fairly decent.
Bloodgruel is particularly of use here. Every time a spell is cast, roll a 2+ and you regain a wound. With the Slaughtermaster's 5 wounds, this becomes quite useful in a fight. (On a roll of 1, not so useful as you take a S6 hit but still have a chance for it not to wound, armour save and ward save). You can go up against another character and heal yourself while buffing your troops. Marvellous!
Add to this that you get +1 to the next spell and this is a very useful attribute, effectively making you a level 5 wizard after the first spell.
Now to the spells:
Signature - Spinemarrow 6+: Stubborn for your unit or another? Very useful for a 6+ spell, considering that leadership is one of the key weak points for OK's. Keeping in mind that it is also a 6+ spell to buff your wizard to a level 5 and regain a wound, it's actually not bad at all.
1. Bonecrusher 8+: A fair attack spell. No one is jumping up and down about 2D6 S2 hits, but when you add no armour saves it becomes a fair attack. Especially against high armour, low toughness troops like Empire Knights, Elves of all kinds, etc. A bit of a high casting price for me, but fair.
2. Bullgorger 7+: Decent buff. +1 strength to unit or 14+ to give to all units in 12 inches. Good for a 7+ casting price. Again, synergy is important here. By itself it's the bad side of okay. But when your wizard can hold his own in combat, so can be on front line where the buff's really matter it becomes a decent spell.
3. Toothcracker 8+: Same as Bullgorger but +1 toughness and for 16+ for all troops in 12". A bit expensive for results, but still decent.
4. Braingobbler 9+: Induce panic test in target unit, except for those Immune to Psychology. Situational for it to be useful. With the right army, like Orc's & Goblins or Skaven, can be very useful. For a lot of armies though it's not useful at all (Elves, Lizardmen, Chaos and any Unbreakable armies like Vampire Counts and Tomb Kings). I'd switch this one for the signature spell.
5. Trollguts 12+: Pricy buff, but 4+ Regen for your unit or target unit? Or everyone in 12 inches?! YES PLEASE! Easily my favourite spell, despite the high casting cost as the Ogre's usually don't have much going for them in terms of high armour saves and this spell could win the entire battle for you as suddenly your troops get an extra edge in combat.
6. The Maw 15+: Direct damage template attack. Based on initiative, if you pass you just get a S3 hit, if you don't, S7 with D6 wounds. Can be good, but you have to roll scatter for placement and this is where it becomes a bit "meh". Overpriced for the likelihood of scattering and doing nothing. You can buff for 21+ and use the larger template to make it more likely, but it's a lot to invest in something that might do nothing. I'd swap this one for signature spell, especially with a high initiative army.
I'd say, from best to worst, is: Spell 5, then 2 and 3 together, then signature, then 1, then 6 and then 4.
I'd look to swap 4 first and then 6. But if I'm going up against O&Gs, then I'd keep the panic spell. If I'm going up against lizardment, I'd keep number 6. There's no spell that's super crappy for me here.
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So, there is an extra note on this lore. Following on from the introduction and based on the wizard being in the frontline, able to heal himself and wear armour, you can also add a Hellheart. Force every enemy magic using in D6x5" to suffer a miscast is deadly. Give to your tooled up wizard, or bluff with a character who can rapidly get close to the enemy wizard and BLAMO! If you have an opponent who knows the item, then double bluff with a decoy who heads towards the enemy wizard and watch them flee. Love this one. Especially with armies who will get their wizards close like High Elves (for the +1 to ward saves) or Chaos armies.
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And finally, I love the humor inherent in the Ogre Kingdom's rules. Not the least of which is here in the Magic, where the subtitle of the lore reads:
"Gut Magic. Gastromancy. Shamanic Victuals."
Absolutely brilliant.