Take it from a Dark Lord who's been there, creating MASSIVE, ANGRY monsters to wreak havoc on your enemy is every bit as fucking tangy and arousing as you think it's going to be and then some. One might even say it's the ultimate expression of Dark Lordery, sending mountain sized abominations unto you deserving foe.
Preferably from a very safe distance.
But let me tell you there are some very serious drawbacks to super sizing a monster, not the least among them is the devastation they can wreak on your own forces in the event they go all panic-frenzy. Remember that your army's average foot soldier can be turned into just as creamy a paste as your Giant Status-Monster turns the enemy regulars into.
If you've done your homework, the Enormous Creature you're employing won't be much smarter than a dog and can't reliably be expected to differentiate one group of tiny screaming things from another. Start creating/breeding intelligent Titano Monsters and you're just asking for trouble...
So let's break this down, the pros and cons of Giant Monstering:
PROS:
1) Destructo-Porn: As a Dark Lord there really isn't anything much more gratifying than to witness a hideous abomination you've brought into being, wading through your enemy's city whose magnificent towers and edifices only reach to your Titano-Beast's genitals as is crisscrosses a path of utter destruction throughout that once great metropolis. If you get your Illusionists to record it, you can replay it on a big screen at your orgies.
2) Motivatin Da Troops: In general having a Titano Monster to unleash upon your foe vastly boosts the morale of you troops, which if you're any good at your job should already be high. Nothing soothes and encourages your average foot fodder more than some towering, bestial monstrosity lurching ahead of them toward a fortified position. The more seasoned among them know of course that the situation will get ugly if the thing takes too much resistance and goes all feral again. If you serve long enough on these battlefields, it'll probably happen.
3) Implied Threat: No one wants to have to try to stop a 500 foot tall, enraged anything from smashing their city walls and knocking a bunch of architecture down. So if you happen to have a 500 foot tall something that can kick through city walls like sandcastles and that seems to enjoy stomping on buildings for whatever reason, then you have what's known as a strong bargaining position.
(see also: "Say that's a nice city ya got dere. Be a shame if a Giant Monster stomped all over it.")
4) Status: Sure you've got all kinds of Infantry, some nifty Calvary units, a few flying buggers and a solid core of Warmagi. You've made a name for yourself in the Dark Lording/Evil Emperoring circles. Lesser D-bags are legitimately and rightfully terrified of you, as they should be. Congrats!
But do you have that towering, five hundred plus foot tall goliath beast-thingy that your closest rivals don't?
Or does your Arch-Rival have a larger Giganto-Critter than you, not matter what scale it's on?
In those cases you've lost the Status battle. And while Status may be fleeting and doesn't in and of itself win wars, once you've clawed, kicked and burned your way to the top of the Dark Lord heap, Status becomes all the more important. A good Malevolent Tyrant will always seek to outdo themself, never resting on their laurels even if they just strangled a hundred people with them.
Cons:
1) Feeding The Damn Thing: Whether it's meat, souls, raw magical energy or what have you, a Titano Monster is going to eat a metric fuckton of it and then some. No matter how much you think it's going to consume, it's best to figure on adding another zero to that total. You simply can't comprehend how much of anything a creature that size requires to continue existing. It's truly staggering.
I can speak from experience as once, in my earlier days I had my Blood Science Magi create me a Balrog-Dragon hybrid critter which in time grew to be just over 300 feet tall. At it's peak mass it required about one hundred cows a day to keep it going. That roughly equals 90-100 tons of meat a day.
Picture a huge valley just teeming with cattle. Cows as far as the eye can see, grazing, mooing, fucking, shitting all over the place, happy as cows can be. Then picture two weeks later and that valley is empty because I fed the entire herd to my Ridiculously Massive Skull-Dragon-Wingy-Thing.
Do you know how longs it takes to grow a herd of cattle 20,000 strong? Quite a while....
Eventually I had to have it destroyed at great expense. It's not like you can just set it free, yell "Go Away" at it and expect it to just walk away sadly, head down. Nope, it's gonna fight you and you'd best have your adult Dark Lord pants on that day....
2) Getting Rid Of It: As aforementioned, unless it's magical and can just be banished back from whence it came, your options are limited. You can, of course, continue to employ it and keep it fed at ruinous expense just for the undeniable pleasure of watching it do it's thing, You're a Dark Lord, it's an option.
But suppose for a moment that you want your empire to flourish and not just become a milking cow for your Destructo-Porn addiction. If the Damn Thing can't be banished back to another plane, what's your next move?
Trying to starve it is a super bad idea. Expecting it to walk away like a Harry and the Henderson's sequel is equally implausible. So you're basically left with terminating it. Killing the big, dumb thing.
Don't feel bad about it, you're evil after all. Just hope you have the metaphorical gun big enough to do the job, tough guy.
In the end, no matter how popular Kaijus', Titans' and other assorted Gigundus Aberrations' are at the moment, they're just a Dark Lording fad that will soon run it's course. Don't be fooled in buying the RV of monsters because they're currently trendy, they depreciate faster than an Orc tavern wench.
Yours in Oppression With Compassion
-Lord Hurderoth
Law His Word Be