Names:
Poltar (basic) and Gaist (stage 1)
Types: Ghost, and Ghost/Steel, respectively. Poltar is merely the helmet; Gaist is the full suit of armor, complete with weapon and such.
Poltar evolves into Gaist at level 36. Both are genderless.
Origin: As for the name origins, it's a corruption of the word 'poltergeist', if you didn't notice.
Abilities: Poltar = Levitate only (User takes no damage from Ground-type attacks); Gaist = Weak Armor (If user is hit with a contact attack, Defense goes down 1 stage and Speed goes up 1 stage; effect activates multiple times with a multi-hit attack) OR Steadfast (If user flinches, Speed goes up 1 stage).
Movepool:
(If two numbers exist separated by a slash, it means the former number means the level at which Poltar learns it, and the latter is when Gaist learns it. A single number means the level for both is the same, and a -- means that stage can't learn it.)
1 Night Shade
6 Withdraw
11 Will-O-Wisp
16 Protect
21 Shadow Ball
26 Wide Guard
31 Hex
--/36 Spear Volley*
41/43 Quick Guard
46/50 Iron Defense
51/57 Flash Cannon
*Spear Volley: BP 25, Acc 100, PP 15, Steel-type, Physical. Hits the target anywhere from 3 to 5 times total. Only the final form gets this move.
TMs:
(Note, this is using my own special TM list, developed for the universe in which I created Poltar and Gaist, with TMs numbering from 1 to 100. It's a blend of all Gen's TM lists, but is identical to none.)
TM04 - Calm Mind
TM06 - Toxic
TM10 - Hidden Power
TM12 - Taunt
TM14 - Blizzard
TM15 - Hyper Beam
TM16 - Light Screen
TM17 - Protect
TM20 - Safeguard
TM24 - Thunderbolt
TM25 - Thunder
TM27 - Return
TM29 - Psychic
TM30 - Shadow Ball
TM32 - Hex
TM33 - Reflect
TM34 - Shock Wave
TM39 - Earth Power
TM40 - Aerial Ace
TM41 - Torment
TM44 - Rest
TM46 - Thief
TM49 - Snatch
TM52 - Focus
Miss Blast
TM53 - Energy Ball
TM58 - Endure
TM61 - Will-o-Wisp
TM63 - Embargo
TM66 - Payback
TM67 - Retaliate
TM69 - Rock Polish
TM73 - Thunder Wave
TM75 - Swords Dance
TM76 - Stealth Rock
TM79 - Dark Pulse
TM81 - X-Scissor
TM84 - Poison Jab
TM85 - Iron Head
TM90 - Substitute
TM91 - Flash Cannon
TM94 - Quick Guard
TM95 - Wide Guard
Stats:
Poltar: 55/55/35/65/70/70
Gaist: 80/120/60/50/95/95
Pokedex:
~Poltar: In old abandoned mansions, where life has long since departed, these creatures can sometimes be seen, kept aloft by a flame that burns within its helmet.
~Gaist: It is bound by an eternal curse to forever defend the home of its long-departed lord. This curse prevents it from leaving, but in return grants it immense power.
Movesets:
Rock Polish
Adamant / Lonely, 252 ATK 96 SPE 160 SPA
Item: Life Orb / Focus Sash
Ability: Weak Armor
~Rock Polish
~Iron Head / Spear Volley
~X-Scissor / Earth Power / Will-O-Wisp / Thunder Wave
~Earth Power / Focus Blast / Will-O-Wisp / Thunder Wave
The aim of this set is simple - use Rock Polish to get Gaist set up as soon as you can, and then just outright sweep. Your STAB move of choice can be either Spear Volley, which can hit anywhere between 75 and 125 BP, and Iron Head, which hits at the low end at 80 BP but has a nice 30% chance of Flinch. Since Gaist's movepool is a bit shallow and really hurts due to not getting Earthquake, the last two slots can be whatever you please. Earth Power is a nasty surprise to things like Jirachi or Heatran sans Balloon, where as T-Wave or WOW can cripple an otherwise devastating sweep against Gaist. Gaist doesn't need too much Speed investment, because after one Rock Polish he'll be outrunning everyone regardless, and you want enough SpAtk investment to dent things.
Swords Dance
Jolly / Hasty 96 ATK 252 SPE 160 SPA
Item: Focus Sash / Rocky Helmet
Ability: Weak Armor
~Swords Dance
~Spear Volley / Iron Head
~X-Scissor / Earth Power / Will-O-Wisp / Thunder Wave
~Earth Power / Focus Blast / Will-O-Wisp / Thunder Wave
This moveset is basically the reverse of the other one. However, instead of trying to go for a speed sweep, it goes for a power sweep instead. Gaist suffers from the terrible illness of not being able to use Steadfast against a Fake Out and get an automatic bonus to Speed, so to make up for that, you will want to give him Weak Armor to get as many Speed buffs as he possibly can. Switching him into a multi-hit attacker, like Cloyster, is a nice strategy, as he can threaten the bivalve right back with a STAB Iron Head or Spear Volley, which will probably send him packing. Spear Volley's usually preferred in this scenario, as in this case you might not necessarily have the speed to pull off the flinch, but overall it's much like the set before it.