Assault Vest The Assault Vest is an item that was introduced this generation which boosts the holders Special Defence by 1.5 times. However this comes at the cost of the use of non-damaging moves, including Protect. The Assault Vest is then a very hard item to use effectively and very few Pokemon can pull it off. However it does have considerable benefits for those Pokemon often turning OHKOes into 2HKOes. Unlike in singles the Assault Vest can't be used to bluff a Choice item as effectively given the risks of switching and revenge killing not being a dedicated role. Rather the Assault Vest can be used to boost bulky attackers Special Defense. Some Pokemon like Tyranitar use it to increase there longevity and give Pokemon like Mega Charizard Y the jump, as it can quite easily take Solar Beam now. Others like Hydreigon use it to survive Draco Meteors, and not get 2HKOed by coverage moves. Building the Correct EV Spread For the most part one can not simply slap on an Assault Vest onto a Pokemon and call it done. If we take the earlier example of Hydreigon we must first identify the goal of the EV spread. As we will be investing in bulk it will be nice to survive Jolly Garchomps Dragon Claw. To guarantee not to be OHKOed you need to run a minimum of 108 EVs in HP. Next lets look into Modest Salamence's Draco Meteor, this can be done with another 64 EVs in HP or alternatively 44 EVs in Special Defense. Calcs (Move your mouse to reveal the content) Calcs (open) Calcs (close) 252 Atk Garchomp Dragon Claw vs. 108 HP / 0 Def Hydreigon: 152-180 (83.9 - 99.4%) -- guaranteed 2HKO 252+ SpA Salamence Draco Meteor vs. 108 HP / 44 SpD Assault Vest Hydreigon: 152-180 (83.9 - 99.4%) -- guaranteed 2HKO 252 SpA Life Orb Tyranitar Ice Beam vs. 108 HP / 44 SpD Assault Vest Hydreigon: 75-91 (41.4 - 50.2%) -- 0.4% chance to 2HKO 252+ SpA Life Orb Tyranitar Ice Beam vs. 108 HP / 44 SpD Assault Vest Hydreigon: 83-99 (45.8 - 54.6%) -- 47.7% chance to 2HKO 252+ SpA Mega Charizard Y Overheat vs. 108 HP / 44 SpD Assault Vest Hydreigon in Sun: 74-87 (40.8 - 48%) -- guaranteed 3HKO 252+ SpA Life Orb Ludicolo Ice Beam vs. 108 HP / 44 SpD Assault Vest Hydreigon: 81-96 (44.7 - 53%) -- 22.7% chance to 2HKO 252 SpA Mega Manectric Hidden Power Ice vs. 108 HP / 44 SpD Assault Vest Hydreigon: 50-60 (27.6 - 33.1%) -- guaranteed 4HKO Given that your running a large amount bulk a Modest nature would be recommended so that you can hit as hard as possible with the EVs remaining. 220 Speed EVs should be run to out speed max Speed base 80s. Leaving 136 EVs to be run in Special Attack. These EVs are more than enough for Hydreigon to pick up OHKOes with Draco Meteor, Fire Blast, and Dark Pulse. Notable Users Hydreigon Set (Move your mouse to reveal the content) Set (open) Set (close) Hydreigon @ Assault Vest Ability: Levitate Level: 50 EVs: 108 HP / 136 SAtk / 44 SDef / 220 Spd Modest Nature - Stone Edge / Dragon Pulse - Draco Meteor - Fire Blast / Flamethrower - Dark Pulse Tyranitar Conkeldurr Azumarill Scrafty Set (Move your mouse to reveal the content) Set (open) Set (close) Scrafty @ Assault Vest Ability: Intimidate Level: 50 EVs: 252 HP / 152 Atk / 68 Def / 36 SDef Adamant Nature - Fake Out - Drain Punch - Crunch - Ice Punch / Stone Edge Clawitzer Set (Move your mouse to reveal the content) Set (open) Set (close) Clawitzer @ Assault Vest Ability: Mega Launcher EVs: 252 HP / 176 SAtk / 68 SDef / 12 Spd Modest Nature - Water Pulse / Hydro Pump / Muddy Water - Aura Sphere - Dark Pulse - Dragon Pulse / Ice Beam Sets for all of the above are coming, feel free to recommend your own.