Umbreon needs Foul Play to function offensively, as Dark Pulse is a weak move on it:
-Wish
-Protect
-Foul Play
-Heal Bell/Toxic
Nature: Calm
EVs: 252 HP/4 Def/252 SDef
Item: Leftovers
Ability: Synchronize
Vaporeon and Sylveon are better Wish users, IMO, because of higher HP and better typing, respectively:
Vaporeon:
-Wish
-Protect
-Scald
-Ice Beam/Toxic/Roar
Nature: Bold
EVs: 248 HP/252 Def/8 SDef
Item: Leftovers
Ability: Water Absorb
Sylveon:
-Wish
-Protect
-Hyper Voice
-Heal Bell
Nature: Bold
EVs: 252 HP/252 Def/4 SDef
Item: Leftovers
Ability: Pixilate
Medicham is too frail for Bulk Up. It's best played as an all-out attacker:
-High Jump Kick
-Fire Punch
-Zen Headbutt/Ice Punch
-Bullet Punch/Substitute
Nature: Jolly/Adamant
EVs: 252 Atk/4 Def/252 Spe
Item: Medichamite
Ability: Pure Power
Ice Shard is kind of unnecessary on Cloyster because of how Shell Smash boosts its Speed:
-Shell Smash
-Icicle Spear
-Rock Blast
-Hydro Pump/Razor Shell
Nature: Naive/Jolly/Adamant
EVs: 252 Atk/4 SAtk/252 Spe
Item: Never-Melt Ice/Icicle Plate/Lum Berry/Focus Sash/White Herb
Ability: Skill Link
A Rapid Spinner would be appreciated on the team to deal with Cloyster's Stealth Rock weakness. Forretress is the best suited one, IMO:
-Stealth Rock/Spikes
-Rapid Spin
-Gyro Ball
-Earthquake/Volt Switch
Nature: Relaxed
EVs: 252 HP/252 Def/4 SDef
Item: Leftovers
Teammates that help out Medicham fill in the last two slot. A slow Volt Switch/U-turn user (like Wash Rotom) gets Medicham in safely without it having to take a hit (Forretress does this too, if you opt for Volt Switch):
-Volt Switch
-Hydro Pump
-Will-o-Wisp
-Pain Split/Rest
Nature: Bold
EVs: 248 HP/216 Def/44 Spe
Item: Leftovers
An attacker that clean up after Medicham has done its job, such as Lucario, Terrakion and Talonflame, can be put in the last slot:
Lucario:
-Swords Dance
-Close Combat
-Extreme Speed/Bullet Punch
-Crunch/Ice Punch
Nature: Jolly/Adamant
EVs: 4 HP/252 Atk/252 Spe
Item: Life Orb
Terrakion:
-Close Combat
-Stone Edge
-Earthquake
-Quick Attack/X-Scissor/Rock Slide
Nature: Jolly
EVs: 252 Atk/4 Def/252 Spe
Item: Choice Band/Choice Scarf
or
-Close Combat
-Stone Edge
-Hidden Power (Ice)
-Earthquake/Protect
Nature: Naive
EVs: 252 Atk/4 SAtk/252 Spe
Item: Life Orb
or
-Stealth Rock
-Close Combat
-Stone Edge
-Taunt/Earthquake/Swords Dance
Nature: Jolly
EVs: 252 Atk/4 Def/252 Spe
Item: Life Orb/Focus Sash
Talonflame:
-Swords Dance
-Flare Blitz
-Brave Bird
-Roost
Nature: Adamant
EVs: 48 HP/252 Atk/208 Spe
Item: Life Orb/Sharp Beak/Sky Plate
Ability: Gale Wings
or
-Flare Blitz
-Brave Bird
-U-turn
-Will-o-Wisp/Tailwind
Nature: Adamant
EVs: 48 HP/252 Atk/208 Spe
Item: Choice Band
Ability: Gale Wings
or
-Bulk Up
-Brave Bird
-Roost
-Substitute/Taunt
Nature: Careful
EVs: 248 HP/176 SDef/84 Spe
Item: Leftovers
Ability: Gale Wings
Umbreon is not supposed to deal damage tho, i want him to be more like a special wall and an annoyer with first using Toxic then wish then protect in order to make the wish heal it and then dark pulse as a filler. I have tried to find foul play in x and y but I can't find it or find a way to learn Umbreon that move. I was thinking about a Smeargle as my baton passer with Shell Smash, King's Wall, Baton Pass and minimize/rock slide.