I am too much of a stalling mastermind
EV's: 252 HP 252 Def 4 SDef
Cosmic Power- Boosts both defenses, perfect for taking tons of hits after setting up
Toxic- Because it's toxic
Sandstorm- Deals even more damage
Stealth rock- More hazards set
This set helps with staying in long and wiping out many different kinds of Pokemon with tons of crippling and damage dealing moves. Set up cosmic power to raise both defenses. Then you can start with either toxic/sandstorm, and then next move set up the other. Then proceed to work with stealth rock. Claydol should be able to take most hits from boosted defenses from cosmic power.
This would be another set for setting up screen
EV's 252 HP 252 Def 4 SDef
Light Screen- For a special defense screen
Reflect- For a physical defense screen
Stealth Rock- After screens are set up, get as many stealth rocks as you can
Explosion- For the final good -bye
This is a great lead Pokemon set. Depending on the opponents Pokemon, you can choose to set light screen or reflect, then the other screen. Then you can proceed with stealth rock up until you can't take anymore moves. Afterwards you blow up right in the foes face for some nice damage.
Finally we have the sweeping Claydol. This set is best used with a trick room partner. I suggest Dusknoir myself
EV's 252 SpAtk 252 Def 4 HP
Calm mind: While defenses are boosted with EV's, you can take most physical hits an then you start setting up for sweeping with special attack and special defense.
Earth Power: Strong power, STAB, has chance of lowering special defense
Psychic: More strong STAB, again has chance of lowering special defense
Shadow Ball: Great coverage, can lower special defense as well, used to deal with psychics and other ghost types