Years ago, Necro was a boy with a dream: To be a famous opera singer. He was kidnapped by the Illuminati (no, seriously), who performed experiments on him to turn him into a superhuman. The experiments were successful, making him stretchy and able to channel electricity. They came with the side effects of him being bald and ugly. While captured by the Illuminati, he got a girlfriend, Effie. With Effie, Necro escaped the Illuminati and is now fleeing from Gill's cronies while planning his opera career.
tl;dr - Capcom employees were high as fuck.
Franchise fans will recognize Necro as having a fusion of Blanka's and Dhalsim's powers. Too bad he doesn't play like either one of them at all. Pressure's the name of the game, and Necro has it in spades. Unfortunately, the parry system works against Necro more than it does for him.
Super Art Selection - Well, don't pick Super Art 2 and you're good. Slam Dance has no range, even though it technically can be combo'd in to. Super Art 1 gets you some cool corner tricks and a great anti-air. Super Art 3 gets you the combination of a short super bar while having enough meter for EX moves. Electric Snake does a buttload of stun damage too, which is never a bad thing. There's good arguments for both Magnetic Storm and Electric Snake, so pick your favorite.
Normals - Necro has two sets of standing normals, one set for neutral and another set for back. s.LP is quick with long range, s.MP is your go-to poke. s.HP has great range, but awful startup and is easily parried and counterattacked. s.LK is bad, s.MK is good for a very long-range poke. s.HK is to catch an opponent jumping, but isn't very good even for that. b.LP and b.MP are good, especially up close, while b.HP is good antiair and is safe on block despite having awful horizontal range. b.LK is Necro's fastest move, and chains into s.MP. b.MK can be used to hit into M Tornado Hook, which is very useful. b.HK is extra antiair, with a better horizontal range than b.HP. While crouching, his LP almost identical to standing. c.MP is even more anti-air. c.HP is another long-range normal, which is almost never used. c.LK is Necro's fastest low attack, while c.MK is a slow, long-range low poke. c.HK, his sweep, is almost unusable due to its slow startup. Elbow Cannon, his down-back HP, is a quick move with good range that knocks down. It can be used as an anti-air, too. Necro's air game is mostly going to be Drill Kicks, but j.MP can be used to maintain pressure while jumping back. j.MK is used to hit opponents above you (although Necro has the highest jump in the game). j.HP is arguably the best air-to-air move in the game. j.HK has great horizontal range and stays out longer than j.HP, making it better to hit grounded targets with. I strongly advise against using light buttons in the air.
- HCF+P - Tornado Hook (EX) - Necro's signature move. Light has quick startup, two hits, and it pops enemies up into the air. Medium has OK startup, two hits, and keeps enemies grounded. Hard has awful startup, hits three times, and turns enemies around after the third hit. All three can be cancelled into super, but SA2 will only connect after the Hard version. EX hits five times and will more than likely end up with an opponent going to the corner.
- QCB+P - Flying Viper (EX) - A jumping overhead move. It's got bad startup and is hella punishable. You won't want to use it more than once or twice in a match, your opponent will get keen to it. Harder versions go further, giving your opponent more time to react. EX isn't worth the meter, although it does hit twice. It DOES NOT track, it goes as far as the hard version, but faster.
- HCF+K - Snake Fang - Necro's command grab. Blockable, but hits low. Unsafe on block. It throws the opponent very far behind you. It can be combo'd in to off of b.MK, but only if the opponent is crouching. Harder versions start slower and do more damage. I think they also reach further, but have a blind spot between Necro's hand and his body.
- QCB+K - Rising Cobra (EX) - Another overhead. Again, not very good. Where Flying Viper makes Necro jump (and therefore immune to lows), Rising Cobra moves Necro's hitbox backwards, protecting him from being thrown. Hard versions have a slightly larger delay but deal more damage, and EX hits twice. Use it about as much as Flying Viper.
- SRK+P (mashable) - Denji Blast - Necro's electricity. Necro steps forward before discharging, so keep that in mind. It's not a bad anti-air and it's very difficult to parry, but it can be beat by a few moves.
- D+K (Air) - Drill Kick - Necro's dive kick. The strength of the kick changes the trajectory of the dive. Light goes horizontally the furthest, while hard goes almost straight down. You only want to use light to escape corners, really, but M and H are valuable pressure tools. The goal is to hit as close to your opponent's feet as you can. While Drill Kick cannot be combo'd after, it's still great to maintain pressure. It won't cross up, so don't think that it will.
Game Plan - Necro is a pressure character. The first goal is to force the opponent into a corner. Use Elbow Cannon, EX Tornado Hook, and Snake Fang to move your opponent to the end of the stage. From there, Necro can maintain pressure with his long-range normals (mostly s.MP and s.MK), his Drill Kicks, and Tornado Hook. If the opponent starts holding down-back too much, throw in a UOH, Flying Viper, or Rising Cobra to remind them you have those moves. Jump-back MP is useful for pressuring taller characters. If they try to jump out, hit them with an air-to-air to push them back into the corner. Necro's normal throw can be combo'd from in the corner, which allows you to run a (poor) reset game as well.
- H Tornado Hook, b.MK, M Tornado Hook xx SA1 or SA3
- H Tornado Hook, b.MK, EX Tornado Hook
- H Tornado Hook, L Tornado Hook
- H Tornado Hook, Elbow Cannon
- H Tornado Hook, SA2
- b.HP, s.MP, SA1
- b.HP, Elbow Cannon
- b.HP, j.LP
- b.MK, Snake Fang (opponent must be crouching)
- b.LK, s.MP, SA1 or SA3
- j.HK, SA1 or SA3
- Denji Blast, s.HP (when opponent is jumping in)
- H Tornado Hook, L Tornado Hook, s.LK
- Normal Throw, Elbow Cannon
- Normal Throw, s.MP, SA1
- Normal Throw, SA1
Basically, in the corner, almost anything that pops the opponent into the air can be followed up with a number of normals (s.LP, s.MP, s.LK, b.LP, b.MP, c.MP).