Ah! Tarrasque!

[focallength]

find out what it eats and put out a buffet table (The terrasque is only active for what? 24 hours and it only wakes up to eat right?) Figure out how far it could travel in a day (realisticly. Its not just going to start a walkabout, itll feed and go back to sleep) warn the appropriate populace it could threaten, and be sure to tell their leaders that some whack job is interested in waking up a doomsday machine. (this should get more than one kingdom on your side, get out your best little black number and prepare for WAR!)

 

[Lasher Dragon]

Its worth a shot, but you dont know if itll even affect him.

I'd call nerve gas poison, and it is immune.

 

[focallength]

that was the other part to the movie quote. If you can find CN20 nerve gas in a D&D setting the terrasque is the least of your worries.
This reminds me, in the old forgotten realms comics some wizard created a spell to control the terrasque (it involved killing a dragon of each color and their heads were used as a component for the spell so.) Oh and no magic missiles theyll just bounce back at you and I think its horns count as vorpal blades. If I absolutely had to fight it I woul work on trying to get it to another dimension or plane. Although as previously stated this will most likely annoy the people who live in the dimension you send it to. Or, you cant kill it without a wish but what if you can keep it at a constant -10 I.E drop it into a volcano. It wont die but it wont get up either (until the bad guys find out where you dumped it and bring it back) Go find some really powerful good guys and tell them whats going on. Im sure Elminster would take an interest in a terrasque. Really theres a ton of ways to deal with it if your not to proud to ask for help. Go get Nato and take over this guys kingdom, sounds like hes got some WOMD to me.

 

[Crothian]

let the Tarrasque capture you all, have it brag and reveal its plans to you, then escape and stop it

 

[Nifft]

Could you plane shift somewhere and then gate Mr. T to you?

-- N

 

[Lasher Dragon]

That would be the preferred method, assuming you can get a Tarrasque through a gate. I kinda doubt it, seeing that the Tarrasque has a space of 30 feet and the gate can only be up to 20 feet wide. Although, I wonder if you could cast a Widened gate....

 

[domino]

Could you plane shift somewhere and then gate Mr. T to you?

-- N

Gate doesn't work against unique monsters.

Would an arrow of magical beast slaying work?

 

[Lasher Dragon]

Where does it say the Tarrasque is a unique creature? I missed that.

An arrow of slaying could bring it to it's HP +10 in subdual damage.

 

[focallength]

it says it in the terrasques background, it is a one of a kind monster and it only wakes ever (going from memory here so forgive me if Im a little off) 100 years to feed and it feeds for 24 hours.

 

[Lasher Dragon]

Ahh the SRD fails to mention the Unique-ness, and being at work that's all I have to go by. So Gate is out - which like I said previously I'm not sure it would have worked anyway. Space 30 feet and it stands 50 feet tall - that'd be one helluva squeeze LOL.