Gastly

Using Gastly in a Playthrough

The Gastly line develops into one of the series' fastest and strongest special-attacking Ghost lines, combining high Special Attack and Speed with useful immunities to Normal and Fighting attacks. Haunter already possesses strong offensive stats after evolving at level 25 and remains a viable playthrough Pokemon when trading is unavailable, while Gengar improves its Speed, power, and durability further. The need to trade Haunter to obtain Gengar is the line's major practical drawback in many games, making Haunter the realistic final stage for players without access to trading. Earlier generations restrict the line more severely because Ghost attacks such as Shadow Ball were physical before the Generation IV physical/special split, preventing Gengar from using its high Special Attack for its primary Ghost STAB; the split dramatically improved its direct offense. Gengar has also benefited from broad special coverage, status and disruption moves, and, in games where it is available, Mega Evolution. Its defensive profile also changes unusually across generations: Gengar possessed Levitate from Generations III through VI, granting a valuable Ground immunity, but from Generation VII onward its ability became Cursed Body and Ground attacks once again became a major threat. In Red, Blue, and Yellow Version, Haunter can be picked up before the 4th gym at lvl 25. Even without access to Gengar, Haunter can still hit very hard with TMs like Thunderbolt, Psychic, Gigadrain. In early gens, Normal moves are very common so Ghost typing is incredibly useful.

Gastly in Competitive Pokémon

Gengar has one of the longest histories of competitive relevance among Generation I Pokemon, with high Special Attack, excellent Speed, immunities, and an unusually broad utility movepool allowing it to function as an attacker, disruptor, spinblocker in older formats, or revenge killer across many generations. Its competitive importance actually begins in Generation I, where Gengar is the only fully evolved Ghost-type and occupies a role unlike anything else in the format. Its Normal immunity lets it completely ignore influential moves such as Body Slam, Hyper Beam, Self-Destruct, and Explosion, while its Speed makes Hypnosis the fastest sleep-inducing move available in standard RBY play. Its high Generation I Speed also gives it a comparatively high critical-hit rate under that game's mechanics, adding another layer of danger to an already unpredictable Pokemon. Smogon describes it as a centralizing threat in ADV and a potent offensive and utility Pokemon in DPP, while later generations continued to use combinations of Shadow Ball, Sludge Wave, Focus Blast, Taunt, Destiny Bond, and other disruptive options. Mega Gengar raised the line's competitive ceiling dramatically through much higher offensive stats and Shadow Tag, which prevented many opponents from switching and made it an exceptionally powerful trapper. Gengar remains physically frail, and its loss of Levitate beginning in Generation VII removed the Ground immunity that standard Gengar possessed during Generations III through VI.

Gastly in Nuzlockes

The Gastly line is a strong but fragile Nuzlocke option whose immunities can create completely safe switches against predictable Normal- and Fighting-type attacks. Haunter remains valuable even without trade evolution because its Special Attack and Speed are already high, while Gengar provides a substantial improvement when trading is allowed; FireRed and LeafGreen community evaluations place both forms favorably despite the pre-split weakness of physical Shadow Ball. Their low physical bulk means unexpected coverage or failed damage calculations can be fatal, and the Poison typing also creates a Psychic weakness that must be respected. One particularly important generational quirk is that evolving Haunter can actually remove a defensive immunity. Haunter retains Levitate in later games, while Gengar has Cursed Body from Generation VII onward, meaning a Haunter that was completely safe from Ground attacks suddenly becomes weak to them after evolving. This makes opponent moveset knowledge especially important in a Nuzlocke and can occasionally make delaying the evolution tactically useful. The line therefore rewards planned switching and offensive play much more than attempting to absorb unknown neutral attacks.

Gastly's body is described as approximately ninety-five percent poisonous gas, with the remaining portion believed in Pokedex lore to consist of souls lost to that gas. The surrounding vapor can cause fainting or suffocation and can expand around targets much larger than Gastly itself. Animated depictions show Gastly creating illusions, changing form, passing through solid objects, and forming temporary hands from its gas, while also portraying some individuals as playful pranksters. Strong winds can disperse its gaseous body, causing groups of Gastly to shelter together under structures such as house eaves.