
Gastrodon-West-Mega
Ability: Sticky Hold/Storm Drain/Sand Force ----> Storm Drain
Typing:
/
Stats:
HP: 111 ----> 111
Attack: 83 ----> 83
Defense: 68 ----> 108 (+40)
Special Attack: 92 ----> 135 (+43)
Special Defense: 82 ----> 108 (+26)
Speed: 39 ----> 30 (-9)
Base Stat Total: 475 ----> 575
Movepool Additions: None
Description: Gastrodon-West-Mega is a threat. It may not have many tools in its bag, but Water/Ground/Ice/Poison covers most of the bulky attackers and walls in OU, and it has enough special attack that it doesn't need type advantages on the frail stuff, it' too bulky to be one-shotted without a grass move and it has Recover. Problem is, no matter what you give up for Recover, you're dropping the ability to hit something.
Ability: Sticky Hold/Storm Drain/Sand Force ----> Storm Drain
Typing:


Stats:
HP: 111 ----> 111
Attack: 83 ----> 83
Defense: 68 ----> 108 (+40)
Special Attack: 92 ----> 135 (+43)
Special Defense: 82 ----> 108 (+26)
Speed: 39 ----> 30 (-9)
Base Stat Total: 475 ----> 575
Movepool Additions: None
Description: Gastrodon-West-Mega is a threat. It may not have many tools in its bag, but Water/Ground/Ice/Poison covers most of the bulky attackers and walls in OU, and it has enough special attack that it doesn't need type advantages on the frail stuff, it' too bulky to be one-shotted without a grass move and it has Recover. Problem is, no matter what you give up for Recover, you're dropping the ability to hit something.

Gastrodon-East-Mega
Ability: Sticky Hold/Storm Drain/Sand Force ----> Water Absorb
Typing:
/
---->
Stats:
HP: 111 ----> 111
Attack: 83 ----> 80 (-3)
Defense: 68 ----> 128 (+60)
Special Attack: 92 ----> 80 (-12)
Special Defense: 82 ----> 142 (+60)
Speed: 39 ----> 34 (-5)
Base Stat Total: 475 ----> 575
Movepool Additions: Refresh, Roar
Description:
252 Atk Kartana Leaf Blade vs. 0 HP / 0 Def Gastrodon-East-Mega: 306-362 (84.2 - 99.7%) -- guaranteed 2HKO
Bulk. That is what this thing is about. Not going down to anything. Sure, it can't hit back all that hard, but it's got Toxic, it's got Scald, it's got enough attacking stats to make use of type advantages and it's got Recover if it can get a free turn.
Ability: Sticky Hold/Storm Drain/Sand Force ----> Water Absorb
Typing:


Stats:
HP: 111 ----> 111
Attack: 83 ----> 80 (-3)
Defense: 68 ----> 128 (+60)
Special Attack: 92 ----> 80 (-12)
Special Defense: 82 ----> 142 (+60)
Speed: 39 ----> 34 (-5)
Base Stat Total: 475 ----> 575
Movepool Additions: Refresh, Roar
Description:
252 Atk Kartana Leaf Blade vs. 0 HP / 0 Def Gastrodon-East-Mega: 306-362 (84.2 - 99.7%) -- guaranteed 2HKO
Bulk. That is what this thing is about. Not going down to anything. Sure, it can't hit back all that hard, but it's got Toxic, it's got Scald, it's got enough attacking stats to make use of type advantages and it's got Recover if it can get a free turn.
252+ Atk Tapu Bulu Horn Leech vs. 164 HP / 92+ Def Gastrodon in Grassy Terrain: 276-326 (68.3 - 80.6%) -- guaranteed 2HKO after Grassy Terrain recovery
+4 252 Atk Tough Claws Charizard-Mega-X Dragon Claw vs. 164 HP / 92+ Def Gastrodon: 348-409 (86.1 - 101.2%) -- 12.5% chance to OHKO
252 Atk Kartana Leaf Blade vs. 164 HP / 92+ Def Gastrodon: 258-306 (63.8 - 75.7%) -- guaranteed 2HKO
252 SpA Choice Specs Greninja-Ash Dark Pulse vs. 164 HP / 252 SpD Gastrodon: 136-162 (33.6 - 40%) -- guaranteed 3HKO
252 SpA Keldeo Secret Sword vs. 164 HP / 92+ Def Gastrodon: 94-112 (23.2 - 27.7%) -- 81% chance to 4HKO
252+ Atk Life Orb Teravolt Kyurem-Black Fusion Bolt vs. 164 HP / 92+ Def Gastrodon: 263-309 (65 - 76.4%) -- guaranteed 2HKO
252 SpA Latios-Mega Draco Meteor vs. 164 HP / 252 SpD Gastrodon: 153-181 (37.8 - 44.8%) -- guaranteed 3HKO
252+ Atk Huge Power Mawile-Mega Play Rough vs. 164 HP / 92+ Def Gastrodon: 190-225 (47 - 55.6%) -- 76.2% chance to 2HKO
252 Atk Pure Power Medicham-Mega High Jump Kick vs. 164 HP / 92+ Def Gastrodon: 241-285 (59.6 - 70.5%) -- guaranteed 2HKO
252 SpA Magnezone Thunderbolt vs. 164 HP / 252 SpD Gastrodon: 182-216 (45 - 53.4%) -- 32.8% chance to 2HKO
252 SpA Choice Specs Tapu Koko Thunderbolt vs. 164 HP / 252 SpD Gastrodon in Electric Terrain: 330-390 (81.6 - 96.5%) -- guaranteed 2HKO
252 SpA Xurkitree Thunderbolt vs. 164 HP / 252 SpD Gastrodon: 224-266 (55.4 - 65.8%) -- guaranteed 2HKO
+4 252 Atk Tough Claws Charizard-Mega-X Dragon Claw vs. 164 HP / 92+ Def Gastrodon: 348-409 (86.1 - 101.2%) -- 12.5% chance to OHKO
252 Atk Kartana Leaf Blade vs. 164 HP / 92+ Def Gastrodon: 258-306 (63.8 - 75.7%) -- guaranteed 2HKO
252 SpA Choice Specs Greninja-Ash Dark Pulse vs. 164 HP / 252 SpD Gastrodon: 136-162 (33.6 - 40%) -- guaranteed 3HKO
252 SpA Keldeo Secret Sword vs. 164 HP / 92+ Def Gastrodon: 94-112 (23.2 - 27.7%) -- 81% chance to 4HKO
252+ Atk Life Orb Teravolt Kyurem-Black Fusion Bolt vs. 164 HP / 92+ Def Gastrodon: 263-309 (65 - 76.4%) -- guaranteed 2HKO
252 SpA Latios-Mega Draco Meteor vs. 164 HP / 252 SpD Gastrodon: 153-181 (37.8 - 44.8%) -- guaranteed 3HKO
252+ Atk Huge Power Mawile-Mega Play Rough vs. 164 HP / 92+ Def Gastrodon: 190-225 (47 - 55.6%) -- 76.2% chance to 2HKO
252 Atk Pure Power Medicham-Mega High Jump Kick vs. 164 HP / 92+ Def Gastrodon: 241-285 (59.6 - 70.5%) -- guaranteed 2HKO
252 SpA Magnezone Thunderbolt vs. 164 HP / 252 SpD Gastrodon: 182-216 (45 - 53.4%) -- 32.8% chance to 2HKO
252 SpA Choice Specs Tapu Koko Thunderbolt vs. 164 HP / 252 SpD Gastrodon in Electric Terrain: 330-390 (81.6 - 96.5%) -- guaranteed 2HKO
252 SpA Xurkitree Thunderbolt vs. 164 HP / 252 SpD Gastrodon: 224-266 (55.4 - 65.8%) -- guaranteed 2HKO

Magcargo-Mega
Ability: Magma Armour/Flame Body/Weak Armour ----> Sheer Force
Typing:
/
Stats:
HP: 60 ----> 60
Attack: 50 ----> 120 (+70)
Defense: 120 ----> 110 (-10)
Special Attack: 90 ----> 50 (-40)
Special Defense: 80 ----> 110 (+30)
Speed: 30 ----> 80 (+50)
Base Stat Total: 430 ----> 530
Movepool Additions: Flare Blitz
Description: 80 Base Speed isn't bad when you can double it with Shell Smash, and at +2 120 base Flare Blitz will murder everything that doesn't resist it.
Ability: Magma Armour/Flame Body/Weak Armour ----> Sheer Force
Typing:


Stats:
HP: 60 ----> 60
Attack: 50 ----> 120 (+70)
Defense: 120 ----> 110 (-10)
Special Attack: 90 ----> 50 (-40)
Special Defense: 80 ----> 110 (+30)
Speed: 30 ----> 80 (+50)
Base Stat Total: 430 ----> 530
Movepool Additions: Flare Blitz
Description: 80 Base Speed isn't bad when you can double it with Shell Smash, and at +2 120 base Flare Blitz will murder everything that doesn't resist it.

Swalot-Mega
Ability: Liquid Ooze/Sticky Hold/Gluttony ----> Semi-Solid Body (Fur Coat clone)
Typing:
Stats:
HP: 100 ----> 100
Attack: 73 ----> 73
Defense: 83 ----> 123 (+40)
Special Attack: 73 ----> 73
Special Defense: 83 ----> 123 (+40)
Speed: 55 ----> 75 (+20)
Base Stat Total: 467 ----> 567
Movepool Additions: Recover
Description: You know that thing back in like Kanto or Johto in the anime where everything Bellsprout tried had no effect on Muk because his body would just bend with the hit to reduce the damage ? That.
Ability: Liquid Ooze/Sticky Hold/Gluttony ----> Semi-Solid Body (Fur Coat clone)
Typing:

Stats:
HP: 100 ----> 100
Attack: 73 ----> 73
Defense: 83 ----> 123 (+40)
Special Attack: 73 ----> 73
Special Defense: 83 ----> 123 (+40)
Speed: 55 ----> 75 (+20)
Base Stat Total: 467 ----> 567
Movepool Additions: Recover
Description: You know that thing back in like Kanto or Johto in the anime where everything Bellsprout tried had no effect on Muk because his body would just bend with the hit to reduce the damage ? That.