How to unlock Gyarados
There is no direct purchase for Gyarados. It appears on the Kanto banner inside the 4★ pool. The 4★ band takes 6.5% of all pulls and holds 211 partners, so one specific Gyarados works out to about 0.0308% per draw. The 70-pull pity counter only applies to 5★ results, so Gyarados has no floor of its own and no targeted pull. A duplicate Gyarados refunds 120 coins at the 4★ rate.
Gyarados stats and rank
The sheet lists Gyarados at 113 HP, 112 speed, ×1.39 attack, ×1.39 physical and ×1.03 special, with 79 defense and 100 special defense — 540 base-stat total. On the three-stat percentile this is 78.4 out of 100, which puts Gyarados at rank 93 of 966 and in tier A. Relative standing explains more than the total here: its strongest slot is physical multiplier (92nd percentile) and its weakest is special multiplier (40th percentile), so it is a specialist rather than an all-rounder.
Best moves in Gyarados's pool
At move level 5 the pool is led by Body Slam at 75.6 damage per 0.71s (147.5 effective DPS, ×1.39 multiplier), then Tackle at 33.6 damage per 0.38s (124.5 effective DPS, ×1.39 multiplier), then Gust at 31.2 damage per 0.26s (123.7 effective DPS, ×1.03 multiplier). 7 of its 17 damaging moves scale with the physical multiplier and 10 with the special one, alongside 5 support moves. Its physical multiplier is the higher of the two (×1.39 against ×1.03), so physical moves convert better. The top option beats the second by 22.9 DPS, which decides slot one and leaves slot two as a judgement call.
Evolution cards for Gyarados
Its starting move, Water Gun, evolves into Scald once the move is at level 5 and you hold the Power card, which boosts attack for that run. Menu upgrades use a separate system and never stand in for Power. 17 of its 22 moves carry an evolution card, across 6 distinct cards (Vigor, Sprint, Power, Reflexes, Armor and Synthesis). The strongest of them is Body Slam at 147.5 effective DPS, so that is the one worth holding a card for first.
Gyarados compared to similar partners
The two closest stat lines in the roster are Ceruledge (-9 HP, +2 speed, same attack multiplier, -15 total) and Braviary (+2 HP, +0 speed, -0.01 attack, -30 total). Against Ceruledge, Ceruledge is 2 speed faster and the two carry an identical ×1.39 attack multiplier, and the rank gap is 51 places. Read those deltas as swap costs, because a gain on one line is usually paid for on another, so neither side is a strict upgrade and the move pools have to break the tie.