This is how The Princesses transfer their magic to Twilight goes in My Little Pony Transformers Prime: Twilight's Kingdom

[Twilight and Optimus race into the castle]

Twilight Sparkle: Optimus and I came as quickly as we could! Is something wrong? Is it the Overlord?

Optimus Prime: If it is then speak away

Princess Celestia: I'm afraid I put too much trust in Discord and the effect that friendship would have upon him.

[As they are talking about this, the Overlord appears at a magic show and uses his tentacles to drain the magic from all the unicorns there and he transforms into his black and gold second form with a purple cape and golden armor and two black legs replacing his tentacles]

Princess Luna: Discord has betrayed the ponies of Equestria and joined forces with the Overlord.

Twilight Sparkle: [gasps]

Optimus Prime: Is there a way we can defeat him?

Princess Celestia: The Overlord has stolen enough magic that he now has the strength to steal flight as well. Without Pegasi to control the weather, there will be no rain in Equestria.

[As they are talking about this, the Overlord appears at an area and the Wonderbolts fly towards him to stop him, but the Overlord uses his sword and shield to hold the Wonderbolts in place and drains their magic through it. The Wonderbolts fall to the ground as the Overlord leaves]

Princess Celestia: There is word he has gone after Earth Ponies as well. Without their strength, they will not be able to tend the land.

Princess Luna: Ponies will no longer be in control of their world. That power will belong solely to the Overlord.

[As they are talking about this, the Overlord appears at the farms and drains the Earth Ponies of their magic through his sword]

Princess Celestia: There is no doubt that the Overlord is after Alicorn magic. With it still in us, we will not be able to stop him from taking it.

Princess Luna: Once it is in his possession, his power will know no bounds, and all hope will be lost.

Princess Celestia: But there is one solution. It is only by making this sacrifice that Equestria and the lands beyond it might be saved. We must rid ourselves of our magic before the Overlord has the chance to steal it from us.

[Twilight and Optimus look at each other]

Princess Luna: The Overlord is set on possessing Alicorn magic. When he comes for us, we cannot have what he is looking for.

Twilight Sparkle: I'm more than willing to do my part and give up my magic.

Optimus Prime: Twilight.

Princess Luna: You misunderstand. Our magic cannot just disappear into thin air. Somepony must keep it safe.

Princess Cadance: That somepony is you, Twilight.

Twilight Sparkle: Why me?

Princess Celestia: We do not believe that the Overlord is aware that a fourth Alicorn princess exists in Equestria. If we transfer our magic to you, the Overlord will not know where it has gone.

Princess Cadance: Do you understand what we're asking of you?

Twilight Sparkle: Yes. It's just... I'm only now learning how to control my own Alicorn magic. To take on even more–

[Cadance comes over]

Princess Cadance: Twilight, you represent the Element of Magic. If there is anypony who can do this, it's you.

Twilight Sparkle: Taking on this task will be one of the most difficult things I'll ever do, but with the help of my friends–

Optimus Prime: I'm afraid that won't be nessecary.

Princess Celestia: I'm sorry, Princess Twilight and Optimus, but you must keep your new abilities a secret. I fear that your friends being aware of your new power could put them at great risk. Do you still think you can take on this responsibility?

[Twilight nods]

Twilight Sparkle: This is the role I am meant to play as a princess of Equestria! I will not fail to do my duty!

Optimus Prime: That's my Equine princess.

Princess Celestia: Then we must begin at once.

[Princess Celestia, Princess Luna, and Princess Cadance surround Twilight and begin the magic transference]

[As the Princesses transfer their magic to Twilight, the Overlord drains more magic and transforms into his third form, which is him possessing Garmadon]

The Overlord: I am nearly in full power. All I need is Alicorn magic. [leaves to steal the Alicorn magic]

[Princess Celestia, Princess Luna, and Princess Cadance lay on the floor after transferring their magic to Twilight and look at her]

[Twilight is overwhelmed by the Alicorn Magic and her eyes and clear white and her mane and tail are flowing. Princess Celestia, Princess Luna, and Princess Cadance continue the transferrence. Twilight calms down and her eyes return to normal and her mane and tail stop flowing and runs to Princess Celestia and embraces her as Princess Celestia stands. Twilight then sees Celestia's cutie mark gone and Princess Luna and Princess Cadance see their cutie marks are gone]

Princess Celestia: [out of breath] It is done.