Name(s): Octillery
Type: Fire/Ice
Justification: Octillery is about the closest I can think of to be a Fire/Ice type, It's a cannon, which justifies the Fire-type, and there's an octopus species called Pareledone charcoti which happens to live around Antartic.
New Moves: Overheat, Ice Shard, Freeze-Dry, Frost Breath, Flame Charge, Flare Blitz, Flame Burst
Removed Moves: Waterfall
Altered Abilities: None
Name(s): Cryogonal
Type: Ice/Fire
Justification: I included the shiny form because it makes it clear that the glowing bits inside Cryogonal are not merely a part of its icy exterior -- they're glowing balls of light (red in the shiny form, like fire). You might think that's a stretch until you realize that Cryogonal
learns Solar Beam...via level-up. No other Ice type can claim this, and the only other ones that learn it at all (via TM) are Snover and Abomasnow, two Grass types. Solar Beam is almost exclusively learned by Pokemon that associate themselves with light, which is in turn represented by fire. This all makes more sense when you realize that in order to drain the temperature to -148 it as its dex entries describe, it's probably absorbing energy (or heat) into itself. Beyond merely representing cold, Cryogonal represents temperature, so Ice + Fire is the perfect fit.
New Moves: Fire Blast, Flamethrower, Ember, Will o' Wisp, Fire Spin, Sunny Day, Overheat
Removed Moves: None
Altered Abilities: +Flash Fire, +Solar Power
Name(s): Inkay, Malamar
Type: Fire/Ice
Justification: Because Malamar is contrary as all get-out! It's all about upside-down, that's-not-how-things-work logic. It's already an undersea squid that isn't a Water type -now it's an undersea squid infused with the freezing temperatures of the deepest sea, ready to lash out with fire and ice to protect itself. Or just to screw with people, because it's still the closest the series has ever come to an actively malevolent Pokemon.
New Moves: Will O Wisp (Castform-Sunny is the only exception), Flamethrower, Fire Blast (Previous two: Rotom-Heat is the only exception), Flame Charge (Heatmor is the only always-a-Fire type case that lacks it), Heat Wave (Only Groudon-Primal, Castform-Sunny, and Rotom-Heat lack it, none of whom is baseline a Fire type), Incinerate (Again, Rotom-Heat is the only exception), Overheat (Rotom-Heat and, again, Heatmor are the only exceptions), Ice Beam, Blizzard, Avalanche (Nearly universal, and Malamar gets Rock Slide), Hail, Icy Wind, Ice Shard.
Removed Moves: Psycho Cut, Psychic, Calm Mind, Psyshock, Reflect, Hypnosis, Power Split, Psybeam, Psywave, Role Play, Dark Pulse.
Altered Abilities: None.
Name Glalie and mega Glalie
New Type Ice/Fire
Justification Glaie reminds me of comets. Comets are made up of Ice, rock and Superheated gases, and as Ice/Rock and Fire/Rock are taken, Ice/Fire fits it. Plus it always had that Fire type ferocity.
Added Moves : Overheat, Fire Blast, Flamethrower, Fire Fang, Will o Wisp, Flame Charge, Flare Blitz, Sunny Day, Incinerate
Removed Moves : Water Pulse
Altered Abilities : +Flash Fire
Name(s): Vanillite, Vanillish, Vanilluxe
Type: Fire/Ice
Justification: Because ice cream is what Vanilluxe is based off of and since ice cream melts, It can be sorta seen as Vanilluxe is a slowly melting ice cream. Also, in Vanillish's dex entries, it is said that it moved to southern areas during the Ice Age and in Vanillite's dex entries, it is said that it is form by melting icicles in the Morning Sun.
New Moves: Will-O-Wisp, Fire Blast, Eruption, Flamethrower, Sunny Day, Incinerate, Icicle Crash, Flare Blitz, Flame Wheel, Flame Charge, Ember, Sunny Day, Morning Sun, Glaciate, Power Gem, Overheat
Removed Moves: Iron Defence, Mirror Shot
Altered Abilities:
Ice Body is now Solar Power and gets Flame Body as a second ability.
Name(s): Lillipup->Herdier -> Stoutland
Type: Ice/Fire
Justification: Stoutland is partly based on St. Bernard dogs which are associated with rescuing people in mountains. The dex mentions Stoutland rescues stranded people in blizzards (being Ice type would let it live in blizzard-prone areas no problem and you can even encounter one in Cold Storage) and its fur warms people up to health during winter (warmth can be associated with Fire type). I imagine its furry body creates a thermal heat to help people recover in cold regions- think of the fur as something that controls/regulates temperature. A few furry mammals are Fire type like Ninetales and Flareon (which mention internal heat) and which include some canine-based Pokemon like Arcanine and Houndoom. It already learns Ice Fang and Fire Fang as Egg moves and the colour scheme is a nice balance for the two types (Brown seems warm for Fire type and Blue/White for Ice). As for moves I've removed any Water type moves and Thunderbolt (Wild Charge/Thunder Fang stay because they make sense). Since Scrappy is mainly for the Normal type it was before, I changed it to Snow Cloak. As for Sand Rush, if Fur Coat is not overpowered then I would like to propose that because of the Dex entries and flavour (Herdier's Dex entry states how hard the fur is as protection). It's not like Fire/Ice is the best defensively anyway that the double defense is too overpowering. Otherwise, maybe Flash Fire is a safer option. Or if you feel Sand Rush does not need to be replaced that's fine too since dogs dig and Stoutland can possibly rescue people even in Sandstorms. Actually, this would make it immune to both Sand and Hail so that could be an interesting option too but I'll let you decide :)
New Moves: Will-o-wisp, Flamethrower, Fire Blast, Incinerate, Overheat, Flame Wheel, Flare Blitz, Flame Charge, Avalanche, Frost Breath, Ice Beam, Blizzard, Hail, Haze, Ice Shard, Icicle Crash, Icicle Spear, Icy Wind
Removed Moves: Rain Dance, Surf, Thunderbolt
Altered Abilities: Scrappy-> Snow Cloak, Sand Rush-> Fur Coat