To be frank great defensive Pokemon involve...
Bronzong (with levitate ability)- hypnosis/ weather condition i.e. rain or sun
- gyroball (sassy or relaxed nature should be used for a bigger impact.
Altaria (natural cure or cloud9) --leftovers item--
-cotton guard < with this and roost your pretty much immune to physical moves
-Draco metoer/ fireblast/dargon pluse< for everything else except steel PKMN
-earthquake< for steels
Umberon (best defense- hard to use thou) --left overs item--
-curse/toxic: curse is hard to come across for umberon so toxic every thing dat isnt immune
-moonlight/ confuse ray: recovery/ confuse ray helps with stall so you recovery more HP while they die
-protect/ confuse ray: stall untill toxic kills em-fun 4 you, but very annoying 4 victim
-payback/snarl/ confuse ray: payback- to avoid taunt issue/ snarl-support/ stall
Shunckle: best defence/ and a complete killer glass cannon if played on offencive
-stealth rock: really hurts fire/ flying and bug pkmn that switch in
- safe guard:support team so no status issues
-struggle bug: useless to have bugbite as shuckles attack sucks, struggle bug is just to make their special attackers useless.
-power trick: for god sake us this risky set after trick room or it will fail.
-bugbite/rock slide/ stone edge
-brave bird <breed with swanna
-stealth rock< tm tutor
Cloyster (jolly)--focus sash-- forgets its crap sp def, its a great physical wall and sweeper
-rock blast<breed with corsola-make sure it has rock blast too.
-icicle spear: make sure your cloyster has skill link the ability- its beasty.
-shell smash: should always be the first move used and focus sash helps you do dat.
Musharna (relaxed/bold/calm)--leftovers/ wide lens--
-trick room/ calmmind
-charge beam/ shadow ball
And thats all my defensive pkmn's AKA a few of the best non legendaries.