In August 2018 Niantic launched the second Special Research Quest - A Ripple in Time. The Quest consists of 8 stages in which you'll have to complete 3 tasks each for your grand prize - an encounter with the Mytical Pokemon Celebi. As of the time of writing of this article this is the ONLY way to catch Celebi in PokemonGO. It's worth mentioning that participants of the GO Fest 2018 in Chicago had a separate 5-Stage Special Research which featured a Celebi encounter - they were able to catch Celebi a month before everyone else.
Some of the tasks require long preparation, and to help our readers equip themselves with the right items in advanced we are going to list all of them. Note that each tasks gives you an XP reward and completing each stage grants 3 additional rewards.
Stage 1 of 8
- Power up a Pokemon 5 times (1,000 XP)
- Battle in a Gym 2 times (1,000 XP)
- Battle in a Raid (1,000 XP)
Completion Rewards: 10 Pokeballs, 1 Fast TM, 1 Super Incubator.
Stage 2 of 8
- Make 3 new Friends (1,500 XP)
- Catch a Pokemon 3 days in a row (1,500 XP)
- Evolve an evolved grass-type Pokemon (1,500 XP)
Completion Rewards: 1 Sun Stone, 1,500 Stardust, 1 Premium Raid Pass.
Stage 3 of 8
- Reach Trainer Level 25 (2,000 XP)
- Use a Sun Stone to evolve Gloom or Sunkern (2,000 XP)
- Hatch 9 Eggs (2,000 XP)
Completion Rewards: Eevee Encounter, 1 King's Rock, 1 Premium Raid Pass.
Stage 4 of 8
- Walk 10km with Eevee as your Buddy to earn Candy (2,500 XP)
- Evolve Eevee into Espeon during the day (2,500 XP)
- Send 20 Gifts to Friends (2,500 XP)
Completion Rewards: Eevee Encounter, 2,500 Stardust, 1 Metal Coat.
Stage 5 of 8
- Walk 10km with Eevee as your Buddy to earn Candy (3,000 XP)
- Evolve Eevee into Umbreon at night (3,000 XP)
- Trade a Pokemon (3,000 XP)
Completion Rewards: 1 Star Piece, 15 Pinap Berries, 1 Up-Grade.
Stage 6 of 8
- Visit Pokestops 7 days in a row (3,500 XP)
- Use 25 Pinap Berries while catching Pokemon (3,500 XP)
- Use special evolution items to evolve Pokemon 2 times (3,500 XP)
Completion Rewards: 3,500 Stardust, 1 Dragon Scale, 5 Silver Pinap Berries.
Stage 7 of 8
- Catch 40 Grass or Psychic-Type Pokemon (4,000 XP)
- Make an Excellent Curveball Throw (4,000 XP)
- Earn a Gold Johto Medal (4,000 XP)
Completion Rewards: 1 Charged TM, 10 Silver Pinap Berries, Encounter with Celebi.
Stage 8 of 8
- Catch Celebi (4,500 XP)
Completion Rewards: 5,500 Stardust, 1 Super Incubator, 20 Celebi Candy.