Ahh Cobalion, a Pokemon that got the short end of the stick when it comes to the Musketeer quad(don't forget about Keldeo guys!). Cobalion's movepool falls a little short in comparison to its stronger counterparts, Terrakion and Virizion(and again, eventually Keldeo). However, this is no reason to be fooled into thinking that it is useless. Cobalion's resistance to Rock Slide also makes it somewhat worth while, since it is a common move running around in doubles and triples, although the other members of the legendary trio also sport this key resistance. When played correctly, Cobalion provides strong offensive and some decent support capabilities.

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- Close Combat / Sacred Sword
- Iron Head
- Stone Edge
- Protect
Item Attached: Fighting Gem / Sitrus Berry
Ability: Justifed
EVs and Nature:
EVs: 4 HP / 252 Atk / 252 Spd
Jolly Nature (+Spd, -SAtk)

Cobalion's best use is for its attacking power. It has great coverage against common threats, but it can sometimes fall short if not given the right support. In the fast-paced doubles metagame where every move counts, it may not always be in your best interest to run it. However, if you're feeling bold, Cobalion is a nice high risk, high reward Pokemon.

Cobalion has a fairly decent movepool that beats a lot of Pokemon. Stone Edge makes Flying-type Pokemon  worry, but its accuracy can be a pain at times. Close Combat is for those who like power, and is the preferred move because hitting hard is important in doubles. However, Sacred Sword is a totally viable option, and it gets a nice boost from Fighting Gem. Iron Head provides another STAB move, and it gives coverage against Pokemon who resist Rock- and Fighting-type moves.

Cobalion's bulk is helpful for taking many of the attacks that come its way in the doubles environment. Although it isn't the strongest Pokemon out there, if played right it can be extremely deadly. With a Fighting Gem boost, Cobalion does tons of damage to even those who resist it. Close Combat with a Fighting Gem boost is insanely powerful. However, the drops in Defense and Special Defense can be a major drawback. If you're one of those players who doesn't like to switch around very much, it may be in your best interest to run Sacred Sword. You miss out on a lot of the sheer power, but in return, Cobalion stays around to take a few more hits.

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- Sacred Sword
- Helping Hand
- Reflect / Thunder Wave / Taunt
- Reflect / Thunder Wave / Taunt
Item Attached: Sitrus Berry / Occa Berry
Ability: Justifed
EVs and Nature:
EVs: 68 HP / 188 Def / 252 Spd
Jolly Nature (+Spd, -SAtk)

Cobalion can also make use of a supportive set. With access to Reflect, Taunt, Thunder Wave, and Helping Hand, Cobalion can serve as a decent doubles helper for a stronger Pokemon. With an EV spread of 68 HP / 188 Def / 252 Spe and a Jolly Nature, Cobalion always lives Terrakion's Close Combat or Conkeldurr's Drain Punch, and can KO Terrakion back with Close Combat, or set up Reflect or use Thunder Wave.

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A more potent option is a Choice Band set. With strong attacks boosted by the Choice Band and good coverage, Cobalion can hit like a truck. However, this leaves it more open to some of the resisters of its dual STAB moves, most notably bulky Ghost-types. With help in eliminating these and proper use of Team Preview, however, Choice Band Cobalion can work excellently. There is also a special side to its attacks, which features Focus Blast and Flash Cannon, as well as Calm Mind. These moves can provide another option to beat more defensively based Pokemon. Chople or Occa Berry are also viable options, as they allow Cobalion to live many of the prevalent Fighting and Fire-type attacks. Swords Dance can also be used for a nice Attack boost, if you find the time to set it up.
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Well BH, there's my piece, hope you enjoyed. PM me back if I missed anything

Also, I didn't get any credit D: