Good starting quest ideas

[shad0w]

I'm trying to start a campaign with about 5 people but i'm having a bit of trouble figuring out a premise. So far we have a Shadar-Kai rogue, a human cleric, a half-elf wizard, a hexblade, a paladin and maybe another tanky build style character. I was thinking perhaps a wizard is trying to rip holes in the planes in an attempt to glean knowledge and power but random low-level monsters are being sucked into our plane. The monsters would get progressively stronger as the rips grow and harder to resist the pull but i'm coming up with blanks for a cool plot twist for how to close them besides killing the wizard and throwing a piece of the offending arcanist through each portal.

[ZamielVanWeber]

A good rule of thumb for me is, if you cannot think of anything else, stat up an elder evil and go from there.

That aside you sound like you have a good starting point; I would recommend you intersperse the main plot with side quests that will occasionally take them into contact with the tears. Let them notice the pattern on their own before questing to end them.

[Theodred theOld]

Perhaps the entity causing the rips is on the other side of the portals and the wizard was just it's agent on this plane. The party kills the wizard only to find out that not only did their plan not work but the disturbances are getting worse. Now they have to find a way to get to the other side and find the real source.

[Geddy2112]

Ditto the above.
For their starting quest, make it something like "a monster just randomly appeared in X". Make it something that is out of place, like a normally aquatic monster in a forest, so it raises suspision that there is a greater force at work. However, the quest giver is the monarch/government/concerned order of ______ which helps introduce the world and universe. Perhaps there are multiple political powers in play, all having different solutions or caring of the problem of random things appearing. Maybe a religious order knows how to stop this, perhaps an ancient artifact is needed.

[Karl Aegis]

They're at a rave in Pandemonium trying to find someone before going to the after-party through an astral portal to the other side of Pandemonium. The fiendish bugbear junkie that you sometimes see in other places (but this one is fiendish) tries to solicit you for drugs. Being Pandemonium, there is a staircase that doesn't obey Euclidean physics. Going up three flights from the first floor brings you to the second floor of the building, and going down one flight from the second floor brings you to the second floor. All other options go to the first floor. You can go down a flight of stairs from the first floor, but you will always end up on the first floor no matter how many flights you go down from the first floor.

[macdaddy]

Perhaps the entity causing the rips is on the other side of the portals and the wizard was just it's agent on this plane. The party kills the wizard only to find out that not only did their plan not work but the disturbances are getting worse. Now they have to find a way to get to the other side and find the real source.

Darn, you beat me to it.

I always like to try and make it "seem" obvious, but then have it be something else. And having some great extra-planer evil appear to be serving a powerful wizard, but actually manipulating the wizard into doing their bidding is amongst my favorites! You can even have the true mastermind appear to help the party by giving them intel because it wants to be free of the wizard and pay him back.... only if the party follows the intel, things get worse.
:)

[shad0w]

They're at a rave in Pandemonium trying to find someone before going to the after-party through an astral portal to the other side of Pandemonium. The fiendish bugbear junkie that you sometimes see in other places (but this one is fiendish) tries to solicit you for drugs. Being Pandemonium, there is a staircase that doesn't obey Euclidean physics. Going up three flights from the first floor brings you to the second floor of the building, and going down one flight from the second floor brings you to the second floor. All other options go to the first floor. You can go down a flight of stairs from the first floor, but you will always end up on the first floor no matter how many flights you go down from the first floor.

I'm definitely using this now, this is ridiculously awesome