Update: Origin Forme Giratina has officially left Pokemon Go, but some new Legendaries have taken its place. The Lake trio from Pokemon Diamond and Pearl--Azelf, Mesprit, and Uxie--have begun appearing in the mobile game, and unlike other Legendaries, they can be encountered in the wild--although they're reportedly very rare and are each only available in a specific region. The original story follows.
Time is running out to catch Giratina in Pokemon Go. Niantic brought the Legendary Pokemon back to Raid Battles earlier this month, this time in its Origin Forme, but it's slated to leave the mobile game once again today, April 29, at 1 PM PT / 4 PM ET, making this your last opportunity to capture one for the foreseeable future.
Unlike Giratina's standard Altered Form--the form it took when it first appeared in Pokemon Go during last year's Halloween event--its Origin Forme is more serpentine in appearance and has offense-oriented stats. In Pokemon lore, this is the form Giratina assumes in the Distortion World--a parallel universe the Pokemon was banished to.
To catch Origin Forme Giratina, you'll first need to travel to a Gym where a Giratina Raid is taking place and team up with other players in the real world to battle it. If you manage to successfully defeat the Renegade Pokemon, you'll be rewarded with a handful of Premier Balls and an opportunity to capture it.
Like its Altered Forme, Origin Forme Giratina is a dual Dragon/Ghost Pokemon, which makes it vulnerable to its own types. Your best bet is to bring along Pokemon like Salamence, Rayquaza, and Gengar, or Dark-types such as Tyranitar and Houndoom. You can read more tips on how to catch Giratina here.
There's no telling yet what Legendary Pokemon will replace Origin Forme Giratina, but a couple of new ones will be available through May and June's Field Research quests. If you achieve a Research Breakthrough during those two months, you'll have a chance to encounter Ho-Oh, Lugia, Latios, or Latias. On top of that, Shiny Meltan is appearing in Pokemon Go again right now, but it'll only be available until May 5.