Through April 30, 2023 at 4:59pm PDT / 7:59pm EDT (23:59 UTC), you can challenge a 7-star Inteleon in Tera Raids in Pokémon Scarlet & Violet. This Inteleon is always an Ice Tera Type and has the Mightiest Mark, granting it the title “Inteleon the Unrivaled” during battle.
Before you can challenge this Inteleon, you’ll first need to have unlocked 6-star Raids, which is something you can do after beating the game and doing some of the postgame stuff. The Inteleon raids will then appear in the Black Tera Raid Crystals on the map similar to the other 6-star Raid Crystals, though you’ll be able to tell it’s Inteleon due to it being Ice Tera Type. Even if you don’t have it unlocked yet, you can still join other players if they have unlocked it and you have the Link Code or are playing with friends.
According to Serebii.net’s coverage, it knows the moves Blizzard, Snipe Shot, Dark Pulse, and Tearful Look. It opens the battle by using both Snowscape and Mist, ensuring its Blizzard will hit with perfect accuracy and also raising its Defense due to the snow, and Mist will prevent any of its stats from being lowered. It also has Sniper for its Ability, which increases the damage it deals by its critical hits.
If you’re looking for a guide for where to EV train your Pokémon to challenge Inteleon, you can refer to Marriland’s Pokémon Scarlet & Violet EV Training Guides, which should help make your job easier by showing you which Pokémon to fight against to quickly and effectively EV train, although it’s up to you to decide which EVs and which Pokémon to use against Inteleon (HP and then either Attack or Sp. Atk is generally a good starting point, though).
After beating it, you can catch it, although keep in mind that you can only catch it once, regardless of how many times you fight it. You can still fight it again for its rewards, though. You’re guaranteed to get an Ability Patch and TM143 Blizzard the first time you defeat it.
This is the first of two runs of this event. Inteleon will appear next weekend as well, from May 4, 2023 at 5:00pm PDT / 8:00pm EDT (May 5, 2023 at 00:00 UTC) through May 7, 2023 at 4:59pm PDT / 7:59pm EDT, although you’ll still only be able to catch it once per game, even during the second run of the event.