In my campaign, I will be pitting a Warlock a Monk and a Dread necromancer against whatever party my group wants to make. The subquest: stop the three from reaching 20 and completing a ritual that will change existance (destroy it, recreate it, dominate it, become gods, undo gods...). The party will be aware of this threat, but it is my hope that they wont be able to do much about it.
While none of their classes are known for being extremely powerful, the three will basically annoy the group while they complete other quests; They might pop in to kill the king who was just about to pay the party, or the team might rescue the party from a a dragon slightly older than the party expected.
Of course, for every one level the party gains, the trio will gain one or two and the they won't be interested in really fighting to make things fair; an eldritch blast here, a grapple there, the occasional stolen and returned spellbook...but they won't stay long and they will try not to actually kill the party.
Now I need ideas as to what the party should be doing while they arent stopping my little team; every problem they face has to be a quest in and of itself, however it must also be something the three can intrude upon to remind the party that they have other problems.
-----IF I can win rock-paper-scissors to be DM, that is.