Ways to challenge my group without overpowering them.

[RndmNumGen]

I'm in the middle of running my first campaign at the moment, and I've noticed a particular trend; the barbarian keeps killing everyone. In fact, he does such an excellent job killing everyone that the ranger, rogue and wizard have little to do; given the campaign is low level(we started at 1, right now two of my players just hit lv3 and the other two are just about to level). In addition, most of the players are new to D&D, with the exception of the rogue, so the game is very low-op.

The barbarian is doing so well mostly because he's a half orc and has a 20 strength. If he can close into things in melee, he can hit and thus beat the crap out of just about anything. In the last session I tried to work around this and provide more challenges that couldn't just be solved just by hitting things: A pit trap went off and landed the barbarian 20 feet down for a good 5 rounds of one fight, an assassin vine grappled him and other characters alternately, and a homebrew creature made judicious use of charm person and lesser confusion SLAs. All of these proved effective, but I'm worried about overusing them or making it seem like I'm picking on the barbarian. The charm person SLA in particular made my players more than a trifle annoyed.

Note that the three fights where the barbarian wasn't able to run up and beat the crap out of monsters, things were very bloody. There were several times characters came very close to death. As such, I don't want to make the encounters tougher(they're already leaning on the high CR side), as it seems the barbarian is actually carrying a lot of the fights. I just want to make challenge the barbarian more while not making it too hard for the other players.

TLDR: The barbarian in a low-level, 4-man party keeps killing everything. How do I challenge him without overpowering the rest of the group(rogue, wizard, ranger)

[RndmNumGen]

Some more information about the party setup:

1) Half-Orc Barbarian. 20 Strength, has a +11 to attack and does 2d6+7 damage per attack. An average of 14 damage will take a chunk out of almost anything I can throw at the party.

2) Dwarf TWF Ranger, using an Urgrosh. Does significant damage, but only about 2/3 as much as the barbarian and hits only half as often.

3) Human Rogue. The only person aside from myself who is familiar with D&D, he is slightly more optimized than the rest, yet still not greatly so. Most of his advantage comes from being prepared, knowing the right questions to ask, and being paranoid.

4) Gnome Wizard. Probably will be dropping out soon, but may have a replacement of an unknown class come in a few weeks. He's been playing the shortest amount of time, is perhaps the least optimized and doesn't fully grasp the power of magic in 3.5. Despite the potential power of wizards with SoL spells, he really doesn't reach that.

[Tvtyrant]

Have group combat and send a damage sponge after him. An Orc party with a tame Giant Slug or Ooze can send the high HD but low CR beasts at him to give him something to smack while they fight with the party.

Honestly in 3.5 solo monsters don't work, they get killed too fast. Just place 1-2 creatures in the party which have high HD for the CR and let the Barbarian barbar all over it while the party gets to enjoy normal enemies.

An example that would play off of the Ooze I mentioned earlier:
Gelatinous Cube (1) It has 54 HP, more then enough to let it sponge.
Ooze Mephits (2) They have smaller amounts of HP (20) and interesting abilities to keep the fight from just being a slug fest.

This might be a little difficult though, as a ECL 6 encounter. You could drop the mephits for something weaker but they probably wouldn't be "oozey"

[RndmNumGen]

Hmm... I have been sending mostly one or two powerful enemies at them. The cube and mephits alone are both CR3, which is the average CR of solo enemies that they have been facing. They have just leveled up though, so maybe I could use more weaker enemies... undead maybe?

[Z3ro]

I'd advocate sending in larger numbers of weaker enemies. The party should be able to handle 8-10 regular orcs, and if the barbarian kills 5, the rest of the party still gets a chance to do their part. This won't work in a few levels, and can get boring after a few campaigns, but killing orcs is a classic for a reason.

[Diarmuid]

If you're sending in CR3 solo monsters against a ECL3 party, you should expect them to steamroll it. Expecially if you're only sending them against something like that once per day.

The DMG has a guide for how much resources an encounter "should" take a party to overcome based on how it's encounter level compares to the party's ECL.

IIRC, an even leveled encounter should take ~25% of the party's resources. If the barbarian is raging, that's his 1/day. If he takes a few hits and gets healed after combat by the cleric, that's probably 20% of the cleric's spells for the day.

The trick is to mix and match even leveled encounters with some higher leveled ones, and as others have stated...one big baddy (unless its the BBEG) is usually going to get trounced by the party due to action economy.

[danzibr]

[...] let the Barbarian barbar all over it [...]

This is a great suggestions.

[ka_bna]

Juvenile version is CR3: http://www.d20srd.org/srd/monsters/arrowhawk.htm
A flying beast that fries with lightning. Combine it with landbound foes, so the Barbarian has at least something to do, and the other PC's have to take the arrowhawk down themselves.

[Hyfigh]

I'd suggest sending more intelligent opponents. The Barbarian is going to 'smish all da bad guyz' that don't know how to handle him. Use humanoid opponents that can disable: wizards, sorcerers, clerics, druids, and even melee-types using nets and the like. You're getting to a point where battlefield control can shut down opponents. Use that to your advantage. Shut down the Barbarian on occasion so that the rest of the group can finish encounters. Also, start throwing in encounters that can't be solved by 'Hulk SMASH!"

Edit: spells like Grease, Glitterdust, various blinds, etc. These will shut him down without killing the party.

[Tokuhara]

I know I revert to this, but here's my 2c:

Put the party in a cave with a wide chasm. Across the chasm is a rope bridge, one person wide. Now, station Kobolds with Heavy Crossbows on the other side. Heck, give them Flaming arrows (non-magic type. As in arrows with kerosene-dipped cloth wrapped around it and lit on fire). This will give the barbarian a few rounds until he can go all ape on the kobolds. maybe even put the kobolds on perches with a single rope ladder up, so the barbarian has to wait a longer while to crush their skulls. This allows the ranger, the wizard, and to a lesser extent, the rogue a chance to pepper them with ranged attacks (magic missile comes to mind) and makes the barbarian wait. Drop a couple stirges and some oozes to occupy the barbarian and you have a clever encounter that plays to the party composition

[Gamer Girl]

You just need more monsters!

Sure a tough barbarian that does 14 damage is going to take out a single monster quick. But remember he can only target one(or maybe two) monsters a round.

For example:Take 10 orcs, each is just as deadly as the next with a greatsword, but the barbarian can only kill one or two a round, no matter how much damage he does. A 5 hp orc just 'wastes' the rest of that 14 damage. Even better is to mix up the orcs levels. Don't make them all Monster Manual mooks. For 10 orcs you can have 5 1st level warriors, 2 2nd level rogues, 2 3rd level fighters, and one 2nd level barbarian. All still weak, but at least half of them can take at least one hit.

When you want to do a 'boss' monster, add in more monsters. But not little ones. You don't want a minotaur with a bunch of goblins, you want a bunch of minotaurs. Just make the other minotaurs weaker then they normally would be. And as the players can't tell a 'weak' minotaur from a 'normal' one, they have to fight them all.

[danzibr]

You could always make replicas of the party and see how they fare against themselves. Have the barbarian one-shot the wizard or rogue, if possible. That would be interesting.

[Dralnu]

1) As people have mentioned, damage sponges. Oozes. Zombies. Preferably stuff that doesn't make the rogue cry though, or enough things that he can sneak attack in a fight so he has something to do. You can even homebrew stuff for this purpose.
2) Multiple CR1 opponents. Have so many that the fight drags out long enough that the barbarian gets fatigued. There is a downside to rage, after all.
3) More fights per day than the barbarian has rages.