Froslass

Snow Cloak
Evasion increases 20% in hail.
Type Tier
Ice / Ghost UU
Statistics
Min- Min Max Max+
HP
70
- 281 344 -
Atk
80
176 196 259 284
Def
70
158 176 239 262
SpA
80
176 196 259 284
SpD
70
158 176 239 262
Spe
110
230 256 319 350
Name Item Nature

Choice Specs

Choice Specs Timid
Moveset EVs
~ Ice Beam
~ Thunderbolt
~ Shadow Ball
~ Psychic / Hidden Power Fighting
6 HP / 252 SpA / 252 Spe

She is fast, yet underpowered, so Froslass is a good candidate for Choice Specs, which gives her a Special Attack stat of 388. A STAB Ice Beam is always a good thing to have and Froslass backs it up with Thunderbolt and a STAB Shadow Ball. The last slot is for type coverage. Psychic takes down Heracross and Infernape and Hidden Power Fighting hits Tyranitar and Weavile. She is still not too impressive in terms of raw power, but her movepool can certainly support this.

Name Item Nature

Choice Scarf

Choice Scarf Lonely
Moveset EVs
~ Ice Beam
~ Shadow Ball
~ Wake-Up Slap
~ Destiny Bond
204 Atk / 112 SpA / 192 Spe

Choice Scarf may seem unnecessary on something so fast, but like many sets that utilize the Speed boosting item, this set gives Froslass the element of surprise. Froslass can be a useful lead with this set, getting the drop on Weavile and OHKOing with Wake-Up Slap and also 2HKOing Tyranitar should it switch in. If it leads you can bring it—or any other troublesome foes, such as Heracross and Metagross—down with Destiny Bond. Ice Beam and Shadow Ball provide insurance against a possible sweep from the likes of Azelf, although they won't OHKO, so you may have to resort to Destiny Bond. Choice Scarf Garchomp is easily outpaced and OHKOed with Ice Beam. Destiny Bond should ensure a kill when you're ready to sacrifice Froslass.

Name Item Nature

Support

Leftovers / Focus Sash / Colbur Berry Timid
Moveset EVs
~ Thunder Wave / Destiny Bond
~ Confuse Ray / Spikes
~ Ice Beam
~ Thunderbolt
6 HP / 252 SpA / 252 Spe

Thunder Wave provides paralysis support to the team. This can work quite well on Froslass as most Ground-types that are immune to it will be loathe to switch into anything with a STAB Ice Beam. Confuse Ray works alongside paralysis to further annoy your opponent and both may help Froslass escape freely from a Pursuit. She is a little too fragile to Spike as effectively as the likes of Skarmory and Forretress, but her immunities to Normal and Fighting—two attack types which are often used with Choice items—can help her lay them down. Destiny Bond takes down a slower foe who Froslass can't kill off otherwise and works OK with Spikes as it may cause switches. Ice Beam and Thunderbolt in the last two slots are to provide type coverage. Leftovers helps recover damage from Stealth Rock, and Focus Sash helps to guarantee a Destiny Bond kill but is unreliable. Colbur Berry can save her from Pursuit once.

Other Options

Taunt, Safeguard or Substitute stops Blissey from paralyzing Froslass. Block can trap a foe so it can be killed off with Destiny Bond. Light Screen is for more team support.

EVs

Her only stand-out stat is Speed, so you should max that out and give her a Timid nature. Her Special Attack needs all the help it can get so it should also be maxed.

The EVs for the Choice Scarf set allow Froslass to OHKO Weavile and outspeed Choice Scarf Garchomp.

Opinion

She has awful defenses, and her typing is a mixed blessing when it comes to compensating for them. The two immunities provided by Ghost typing are a big help, but this also makes her incredibly vulnerable to Pursuit. Ice typing is fraught with problems, having only one—albeit useful—resistance to itself and giving Froslass many unwanted weaknesses, notably to Stealth Rock. All in all, Froslass' chances of surviving for more than few rounds are low. Access to BoltBeam and ParaFusion do count in her favor, though, and she can be used to bring down some big threats with her excellent Speed and Destiny Bond.

Counters

Pursuit users are a huge problem, especially as she has trouble killing most of them. As such, Weavile, Tyranitar, Heracross, and Metagross can all put an end to Froslass.

Blissey walls Froslass easily (Wake-Up Slap is a 4HKO at best) but can't do anything back in return except paralyze her. Snorlax works much better and can kill with Crunch or Pursuit.

Froslass will come to a fiery end should Heatran or Houndoom appear. Most other Fire-types can take her quite well, but the two listed have the advantage of resisting both her STAB moves. Wake-Up Slap will 2HKO Houndoom, though.

Any remotely powerful super effective attack should kill Froslass easily; her defenses are that poor.