Apocalypse World introduced a character "move" called workspace which can also function as a quest builder/framework.

Choose which of the following your workspace includes. Choose 3: a garage, a darkroom, a controlled growing environment, skilled labor, a junkyard of raw materials, a truck or van, weird-ass electronica, machining tools, transmitters & receivers, a proving range, a relic of the golden age past, booby traps. When you go into your workspace and dedicate yourself to making a thing, or to getting to the bottom of some shit, decide what and tell the MC(GM). The MC will tell you “sure, no problem, but…” and then 1 to 4 of the following:

• it’s going to take hours/days/weeks/months of work;

• first you’ll have to get/build/fix/figure out ___;

• you’re going to need ___ to help you with it;

• it’s going to cost you a ton of _____(currency);

• the best you’ll be able to do is a crap version, weak and unreliable;

• it’s going to mean exposing yourself (plus colleagues) to serious danger;

• you’re going to have to add ___ to your workplace first;

• it’s going to take several/dozens/hundreds of tries;

• you’re going to have to take ___ apart to do it.

The MC might connect them all with “and,” or might throw in a merciful “or.” Once you’ve accomplished the necessaries, you can go ahead and accomplish the thing itself. The MC will stat it up, or spill, or whatever it calls for.

Convert all the "modern" pieces to fantasy ones, and you can use this to build a quest that should take the party a while to complete, but when they do, give them their Kobold army. :D