Hello, this is my first time building a competitive team in any Pokemon game. So far I've breed the following Pokemon and I'm looking for advice on the final slot. I'm also up for any guidance or areas of improvement that can be made in the team, I'm not against replacing some of the Pokemon I've already breed if it improves the effectiveness of the team overall.
Hydreigon
Nature: Modest
EVs: 252 Speed / 252 Special Attack / 6 Special Defence
IVs: 31/x/31/31/31/31
Item: Life Orb
Ability: Levitate
Dragon Pulse
Dark Pulse
Flamethrower
Focus Blast
Blissey
Nature: Bold
EVs: 252 Hp / 252 Defence / 6 Special Defence
IVs: 31/x/31/x/31/x
Item: Leftovers
Ability: Natural Cure
Wish
Seismic Toss
Toxic
Aromatherapy
Conkeldurr
Nature: Adamant
EVs: 252 Attack / 252 HP / 6 Special Defence
IVs: 31/31/31/x/31/31
Item: Flame Orb
Ability: Guts
Drain Punch
Ice Punch
Facade
Mach Punch
Ferrothorn
Nature: Relaxed
EVs: 252 HP / 252 Defence / 6 Special Defence
IVs: 31/31/31/x/31/0
Item: Leftovers
Ability: Iron Barbs
Stealth Rock
Power Whip
Gyro Ball
Leech Seed
Reuniclus
Nature: Bold
EVs: 252 HP / 252 Defence / 6 Special Defence
IVs: 31/x/31/31/31/x
Item: Leftovers
Ability: Magic Guard
Calm Mind
Recover
Psychic
Focus Blast
Some ideas I've had for the final slot include Gyarados, Magnezone, Scizor, Starmie, Mamoswine.
I'd really like to hear peoples thoughts on the team and what Pokemon can fill that final slot, thanks a lot.