Moves
Azelf is one of the premier Stealth Rock setters in the metagame due to its Speed and great movepool. Once Azelf has set up Stealth Rock, Azelf's Explosion has two functions: it heavily damages every non-Ghost-type and lets in another threat to immediately gain momentum as a free switch. Explosion also OHKOes every Rapid Spin user in the game besides Forretress, which can not spin Stealth Rock away due to being slower. Even an Explosion on Normal-resistant targets such as Metagross, Bronzong, and Heatran can open up the opposing team. Another main Azelf role is Taunt, which helps keep Stealth Rock and other entry hazards off the field as well as preventing setup from leads like Gyarados and Dragonite.
As Stealth Rock, Taunt, and Explosion make up Azelf's main niche as a lead, the last slot is more flexible. One great option is Thunder Wave, as Azelf can spread paralysis effectively instead of using Explosion immediately. Common scenarios to use Thunder Wave include against Ghost-type Pokemon such as Rotom-A and Gengar coming in to block Explosion and paralyzing common defensive Pokemon resistant to Explosion such as Jirachi and Choice Scarf Tyranitar. U-turn is another useful move from the lead position, as it allows Azelf to break opposing Focus Sashes and scout out opposing Steel-types, Ghost-types, and Tyranitar trying to Pursuit trap it. Fire Blast directly threatens Steel-types such as Metagross, Skarmory, Jirachi, and Forretress. Make sure to use a Timid nature if using Fire Blast, as Azelf's Explosion is still strong even with a hindering nature.
Set Details
Azelf has a myriad of different EV spreads to adapt to the metagame. Focus Sash is extremely useful for powerful attacks that OHKO Azelf regardless of its EV spread, such as Latias's Choice Specs Draco Meteor. Maximum Speed lets Azelf at least Speed tie with itself and outspeed Gengar, Latias, and Infernape, while HP investment helps Azelf avoid 2HKOes from attacks such as defensive Empoleon's Surf. Azelf can also use a Focus Sash with no bulk to power up Explosion; however, without HP investment, Focus Sash leads Azelf to be vulnerable to offensive leads with priority moves such as Metagross's Meteor Mash + Bullet Punch, Empoleon's Hydro Pump + Aqua Jet, and Machamp's Payback + Bullet Punch while also being vulnerable to Tyranitar's sand, giving it only one turn to do anything. Another choice is 184 HP / 188 Def / 136 Spe. This particular EV spread gives Azelf the ability to survive Choice Scarf Tyranitar's Crunch while also outspeeding positive nature maximum Speed Jirachi, Zapdos, and Flygon. This spread prevents Azelf from fainting to almost all common attacks in the metagame without a Focus Sash, allowing it to use Explosion after it sets up Stealth Rock. Azelf can run many different items as well. Lum Berry prevents lead Breloom, Jirachi, and Uxie from statusing Azelf while also preventing Machamp's confusion. Colbur Berry allows Azelf to survive the strong Dark-type attacks from Tyranitar and Machamp that often prevent Azelf from doing anything beyond setting up Stealth Rock. Sitrus Berry's 25% heal gives Azelf some flexibility in EVs, allowing it to survive various priority such as from Machamp and Metagross as well as Tyranitar's sand from KOing Azelf after a strong hit.
Other EV spreads are viable—note all of these have a Jolly nature: these include outspeeding the positive nature base 90 Speed benchmark such as 228 HP / 216 Def / 8 SpD / 56 Spe that survives Choice Scarf Tyranitar's Crunch + Sand damage and Roserade's Leaf Storm, 252 HP / 56 Def / 64 SpD / 136 Spe outspeeds up to positive nature base 100 Speed Pokemon as well as survive Machamp's Payback and Modest Zapdos's Choice Specs Thunderbolt, 44 HP / 248 Def / 216 Spe that outspeeds Gengar and gives the maximum chance to survive Choice Scarf Tyranitar's Crunch, and 8 HP / 248 SpD / 252 Spe with a Colbur Berry that survives various Dark type attacks and Metagross's Meteor Mash and has maximum Speed.
Usage Tips
Azelf is primarily used as a lead: it sets up Stealth Rock, prevents set up with Taunt, and then uses Explosion. How aggressive to be with Taunt to prevent setup largely depends on how weak to Stealth Rock and other entry hazards the rest of Azelf's team is, Azelf's bulk, and how threatening the opposing lead is to the rest of the team. Hyper offense teams with Dragonite, Gyarados, and Zapdos struggle when they lose a quarter of their health to Stealth Rock, so Azelf should aim to use Taunt on potential Stealth Rock users aggressively, even potentially forgoing Stealth Rock or Explosion. However, bulky Azelf sets can be more forgiving should the opposing lead attack instead of setting up—as an example, physically bulky Azelf can comfortably use Taunt + Stealth Rock on Metagross, as Meteor Mash + Bullet Punch will not KO, but less bulky Azelf are much more at risk. Beware of opponents taking advantage of Taunt and switching to a Choice Scarf Tyranitar and preventing Stealth Rock. Explosion is often very predictable from Azelf, so mixing up the timing of the Explosion such as using Thunder Wave or U-turn on a Ghost-type switch-in can often lead to large payoffs. Fire Blast is often unexpected from Azelf, so hiding it often allows Azelf to do a lot of damage to bulky Fire-weak Pokemon such as Metagross and Forretress.
Team Options
Azelf is a cornerstone of the hyper offense play style in DPP OU—common teammates on these types of teams include Dragon Dance Gyarados, Dragon Dance Dragonite, Dragon Dance Tyranitar, Agility Metagross, Swords Dance Lucario, Swords Dance Scizor, and Swords Dance Empoleon. Azelf immediately gets these threats Stealth Rock and a free switch to start setting up. This setup is especially crucial for Gyarados and Dragonite, as it prevents them from having to deal with Stealth Rock. Azelf's Explosion also commonly targets Steel-types, meaning Dragonite has fewer Dragon-resistant Pokemon it needs to punch through. Azelf also is great for offensive paralysis teams, as it is effective at spreading paralysis on hard-to-paralyze threats such as Rotom-A and Gengar. Common teammates include Jirachi, Machamp, Tyranitar, Breloom, Gyarados, Dragonite, and Latias. Jirachi is particularly effective; Jirachi's Iron Head is not only an effective tool at flinching down paralyzed threats, but mixed Jirachi is very good at breaking threats hard to handle for hyper offense, such as Skarmory and Gyarados with Thunderbolt, Swampert with Grass Knot, and Lucario with Hidden Power Ground or Fire Punch. Jirachi and Latias can also use Healing Wish to open up another attempt from a sweeper such as Gyarados.
Azelf often immediately attracts in Tyranitar to remove it, and as such, that can help Gengar, Calm Mind Jirachi, Zapdos, and Latias break past it once it paralyzes Tyranitar or uses Explosion. Zapdos also benefits from Azelf's ability to prevent Stealth Rock. Azelf's ability to prevent Toxic Spikes in the short term against Roserade and Nidoqueen is critical for Pokemon such as Dragon Dance Tyranitar and offensive Calm Mind Suicune. Azelf can also support teams built around Explosion, such as with Magnezone, Metagross, and even Choice Scarf + Copycat Lucario. Magnet Rise Magnezone works well with Azelf with U-turn, as Bronzong and Metagross will never use Earthquake on Azelf, while Skarmory gives easy entry, allowing Magnezone to trap these Pokemon. Magnezone also traps Choice Scarf Jirachi using Iron Head. Most offensive Pokemon in the tier can pair well with a free switch and Stealth Rock; good teammates can help to mitigate various matchups for hyper offense teams.