Few ideas here:
Wallsharna
EV:s 4 Hp,252 Def, 252 Sp.Def
Nature: Bold, Relaxed, Calm, Sassy
Synchronize/Telepathy
Item: Leftovers
Barrier/Reflect
Calm Mind/Light Screen
Psychic/Psyshock
Signal Beam/Hidden power Fighting
This set is based on defensive capabilities of Musharna.
Boosted with Calm Mind it can also strike back with it's repectable Sp. Attack
Psychic is better than Psyshock and Signal Beam is for Dark types but HP Fighting can also knock out problematic Steel types.
Baton Passharna
EV:s 4 Hp, 252 Def, 252 Sp.Def (can be spread differently)
Nature: Bold/Relaxed/Calm/Sassy
Items: Leftovers/Focus Sash
Calm Mind
Barrier/Substitute
Baton Pass
Stored Power/Psychic/Future Sight
Glaceon as father can produce cool baton passer with Reflect. Sets up special sweeper very nicely. Substitute can replace Barrier as well.
Stored Power before passing makes awfully lot of damage.
It can also attack with Psychic or leave Future Sight waiting to help in sweeping.
Special Attacker
EV:s 4 Hp/Def, 252 Def/Sp. Def, 252 Sp.Att
Nature: Modest/ Quiet
Item: Wise Glasses
Calm Mind
Psychic
Hidden Power Ice/Fighting/Energy Ball
Shadow Ball/Signal Beam
Boosted with Calm Mind Psychic works very nicely and Signal Beam/HP Fighting takes care of the Dark types.
Shadow Ball is another option to take care of other Psychics along with forementioned Signal Beam
Energy Ball is viable option along with HP Ice that knocks out Dragons.
Musharna in it's element
EV:s 252 Hp, 4 Def/Sp.Def/252 Sp.Att
Nature: Modest/ Quiet
Item: Leftovers
Yawn/Hypnosis
Dream Eater/Nightmare
Psychic
Signal Beam/HP Fighting
I had to add some set with sleep-moves. Yawn takes more time but hits always or forces to switch.
Nightmare and Dream Eater of course require those sleeping moves and will miss if foe switches.... but this is Musharna after all
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Psychic is more reliable damage along with something for dark types and other problems such as Steel-types and other Psychics
Musharna sweeping(?)
EV:s 4Hp, 252 Sp.Att,252 Spd
Nature: Modest, Naive, Timid, Hasty
Item: Choice Scarf
Psychic
Signal Beam
Hidden Power Ice/Fighting
Shadow Ball
Surprising more than actually working set for Musharna I fear.
It probably still lacks the necessary speed for sweeping, but fast Musharna may surprise your foe.
Specsharna
EV:s 252Hp, 252 Sp.Att,4Sp. Def/Def.
Nature: Modest/ Quiet
Item: Choice Specs
Psychic/Psy Shock
Shadow Ball/Energy Ball
Hidden Power Ice/Fighting
Signal Beam
Pretty much same as the sweeping attempt only without sweeping attempt and with more punch for Sp. Att.
Other viable options: Moonlight (for defensive walls to keep them up), Protect(same purpose), Toxic, Thunder Wave, Swagger, Trick Room, Heal Bell, Gravity