Over the course of season one it seemed as though Twilights repertoire of magic was rather narrow, but as season two has progressed she has gained more and more magical power. She can perform time and space travel, force fields and the like.
Is there any indication of a grade or power level she has achieved? Perhaps in a letter from Princess Celestia? Is her level of magical aptitude normal for a unicorn?
Is there any indication of a grade or power level she has achieved? Perhaps in a letter from Princess Celestia?
The only thing offhand I can think of that would fit this description is her status as Princess Celestia's apprentice/most loyal student (see the character sidebar and summary on Twilight Sparkle's fandom page).
Twilight Sparkle is a unicorn pony who is a special and loyal apprentice of Princess Celestia [...]
Is her level of magical aptitude normal for a unicorn?
She's actually quite capable with magic in contrast to most unicorn ponies, who usually only get a basic couple of powers (mainly telekinesis AFAICT) and one or more special spells related to their cutie mark (for example, Rarity's gem finding spell).
She has shown that there are limits to the power she can exert (only barely being able to levitate the Ursa Minor back to its cave in Boast Busters being a prime example), and she's demonstrated that she can quickly learn even complex spells (glancing at the time travel spell scroll in It's About Time, then nearly immediately casting it).
As far as present limits, it seems to vary based on the spell in question. A few examples:
As a more general statement, I would speculate that Twilight is running into spell limits before she's running out of energy to execute them (given that she easily cast the aforementioned time-travel spell, and the only thing stopping her from reusing it is the spell's once-per-caster limit). Just conjecture though, since the science of unicorn magic isn't well defined to us viewers.
Twilight is exceptional in regard to magic, having dedicated herself to studying the art. Spike mentions in Boast Busters that Twilight's magical ability is exemplary, and Princess Celestia comments about Twilight's enormous raw magical power in The Cutie Mark Chronicles. Unicorn magic requires concentration and effort, as Twilight explains to Spike at the beginning of Feeling Pinkie Keen and to the Cutie Mark Crusaders in Call of the Cutie, [...]
Twilight is shown developing her skills in a flashback in The Cutie Mark Chronicles, where she has some difficulty using magic to turn a page in her book; the scene shows her progressing in her studies, a theme which continues throughout the series.
Twilight possesses the ability to teleport, which was also common among previous-generation My Little Pony unicorn characters. She first teleports on the show in Friendship is Magic, part 2 when she charges Night Mare Moon and disappears only to reappear behind her and next to the Elements of Harmony. She teleports short distances in Applebuck Season to get ahead of Applejack trying to confront her about her over-exertion, and she unintentionally teleports with Spike from the thoroughfare into her library in The Ticket Master, which leaves Spike slightly singed. She teleports multiple times in Lesson Zero, seemingly without effort. As seen in Secret of My Excess, she is able to teleport other beings as well, teleporting Spike several times to clean a lipstick mark off his cheek.
[quotes sourced from the My Little Pony wiki]
As the seasons progress, Twilight's power grows.
Notice the spell of teleportation:
Her power was way beyond that of any normal unicorn during the whole timeline of the story, even fairly early on, as is clearly outlined in Boast Busters (S1E6) when she hypothesizing that since most unicorns have assorted talents aided by their magic, and Twilight's special talent is magic, her skill exceeds that of everypony else. Nevertheless, this isn't purely inborn. S1E16 - Sonic Rainboom - reminisces at her as a small filly struggling to flip a page in a book using her magic. Then, the rainboom wakes her potential up, but it still takes years of careful study that let her master that magic - and her studies in Ponyville are just another phase on her way to ascension.
Events of S4 finale shed some light on her power levels as alicorn: they are similar to power of other princesses, and considering the even match against Tirek while wielding power of all four - alicorn power is about one fourth the power of the whole pony population of Equestria.
Note that independently from her "normal" unicorn/alicorn magic, while in cooperation with the rest of mane 6, Twilight wields a separate type of magic - the magic of friendship - and it's a game-breaker power, implied to be limitless: "There is magic without the end".
Twilight has always possessed a much higher than usual level of raw magical potential (S1E25 The Cutie Mark Chronicles), with Celestia stating that:
You have a very special gift. I don't think I've ever come across a unicorn with your raw abilities.
Keep in mind that Celestia was well over 1000 years old when she said this, and knew legendary unicorns like Starswirl the Bearded personally, so coming from her this statement means a lot.
Twilight and Spike later elaborate on this in Boast Busters (S1E6), stating that most unicorns only possess a small amount of magic related to their unique talents:
Spike: Twenty-five, Twilight. Twenty-five different kinds of tricks and counting. I thought unicorns were only supposed to have a little magic that matches their special talents!
Twilight Sparkle: True, for ponies whose talents are for things like cooking or singing or math. But what if a unicorn's special talent is magic?
Your perception that Twilight's magical powers have grown over time however is also correct. Since Twilight first took on her role as Celestia's student, her skill at utilizing various spells to perform feats of magical strength has improved considerably.
A couple examples:
Back when Twilight was still quite young, she struggled to perform even a simple levitation spell (S1E25 The Cutie Mark Chronicles). Later, she is able to, with considerable effort, use that same spell to levitate a large magical creature (an Ursa Minor) and the town's water tower a considerable distance (S1E6 Boast Busters).
In Season 1 Episode 2 (Friendship is Magic), Twilight needs to power up and concentrate in order to teleport herself a short distance in front of her. Later she accidentally teleports herself and Spike a longer distance, with unfortunate side effects for Spike (S1E3 The Ticket Master). The very next episode we see Twilight casually teleporting herself around during a conversation with one of her friends (S1E4 Applebuck Season), and eventually we even see her cast a mass teleport (S2E21 Dragon Quest), taking herself, three other characters, and an egg a very significant distance (all the way out of a forest). She continues to cast teleport spells frequently throughout the series, sometimes casually (S4E21 Testing Testing 1, 2, 3), sometimes seemingly without thinking (S4E1 Princess Twilight Sparkle), and sometimes to get herself out of sticky situations (S5E21 Scare Master), demonstrating that she's mastered this ability.
In these situations it appears that it's not so much Twilight's level of magical power increasing as it is her skill with each individual spell.
As of Season 6 Twilight has demonstrated skill with a wide variety of spells, ranging from force fields to gravity manipulation to brainwashing. /u/selfproclaimed on Reddit has compiled an extensive list of these abilites. Here is the section from that list related to magic:
As a member of the unicorn race, Twilight can manifest her inherit magic into a multitude of spells through her horn. Through her years of study and hard work, Twilight’s spellcasting abilities far exceed those of any naturally born Unicorn for at least a thousand years. She is capable of copying any spell she's seen, sometimes even improving it, even if she has only seen it once before and a type of magic she is unfamiliar with.
Concussive blasts
Intercepts and matches a blast from Chrysalis. IDW
This attack can be used to hit multiple targets at once. Twilight can vary the power of it to have it merely stun or hurt a target. That being said, Twilight has never demonstrated this to have the same destructive capability while targeting multiples, so it is very possible that by doing so she sacrifices power. IDW
There is a variation that allows Twilight to encase a target in crystal. FIM
Force Field
Strong enough to block a concussive beam fired by Starlight Glimmer FIM
- For comparison, Starlight's concussive beams are powerful enough to blast apart a huge chunk of a stone bridge FIM
Capable of creating force fields up to sizes large enough to surround a building.. FIM
Has a similar "Bubble of Silence" Spell that contains all sound within the force field. FIM
Teleportation
Teleported four targets, including herself, out of a forest while sprinting.. FIM
Teleported six targets, including herself, from a prone position FIM
Can Summon a Parasprite, a small matter-eating being capable of multiplying infinitely FIM
Telekinesis
After a dam broke, Twilight levitated every last piece of the structure and moved it against the water pressure and repaired the dam in seconds. FIM
Capable of lifting liquid matter, while manipulating herself to stand on water. FIM
Able to utilize it as a stasis spell to stop multiple targets FIM
However, the more targets she's stopping, the more effort she needs to exert as seen when she was struggling to hold two families in place. FIM
Transmutation
Capable of transforming small objects or creatures into an orange FIM
Has a similar spell that can turn creatures into apples. IDW
Is stated to have once transformed half a classroom into plants. IDW
Miscellaneous Spells
Can manifest herself within a book for several minutes as an illustration. This illustration can communicate with the outside world. The spell was originally used to speed up the process of information gathering from a book. To quote Twilight "I've been studying a new studying technique...You'd be amazed what you can pick up when you're actually in a book." FIM
[Sentience Inducement] Come to Life Spell can automate simple machines to move on their own. FIM
[Phasing] Can utilize magic to phase through solid material. FIM
[Gravity Manipulation] Capable of using a spell that changes her own gravity polarity. FIM
[Brainwashing] Want It Need It Spell causes anyone, excluding the caster, to become obsessed with a target object upon eye contact FIM
[Brainwashing] Can reprogram a creature’s dietary nature. FIM
[Mind Delving] Magical Mindscape Manifestation spell allows Twilight to enter the mind of a subject. The resulting mindscape reflects a person’s life and personality and even contains beings that reflect a person’s multiple moods and “sides” of themselves. IDW
[Time Travel] Can go back in time, but can only stay in the past for about a minute before she is brought back to the present. FIM
[Pyrokenesis] Lights an Olympic-like cauldron. FIM
[Voice Manipulation] Increased the volume of her own voice to be heard by opposite ends of a valley. FIM
[Recording] Capable of recording audio and video which can then be displayed like a projector. FIM
[Traumalocation] "Traumalocation" spell, when cast on someone who has recently been the victim of some form of attack, can be used to locate and view the person or persons who committed the act. IDW
[Mind Melding] Spell that combines the consciousness of another character into the caster's own body. IDW
[Speed Enhancement] Twilight can magically accelerate her own speed that allows her to fly at supersonic speeds. The shock wave produced has a strong enough push to knock someone off their feet. IDW
[Magic Sealing] Twilight can take a target's ability to cast magic completely away, though the effect is temporary. IDW
