This is how Tirek takes Celestia's magic goes in My Little Pony: Endgame.
[Tirek goes over to Celestia's unconscious body]
Tirek: You're weak, Celestia and you always will be.
[Shockwave shocks Celestia, knocking her unconscious. Princess Celestia's horn then lights up]
Megatron: Excellent. Everything is going as planned.
[Starscream lands on top of Megatron and knocks him down]
Starscream: Unless, it is interrupted by your former second in command.
[Lugnut punches Starscream]
Lugnut: Megatron will pay for he envious act.
[Tirek punches Lugnut]
Tirek: I will protect you, Starscream.
[Princess Celestia's magic comes out of her horn and flows towards Tirek. Tirek turns around to absorb it and Celestia's magic goes in his mouth and flows into him. Starscream gets up and watches Tirek get Celestia's magic]
Starscream: Why do you need magic to make you stronger?
[Tirek finishes sucking out Celestia's magic]
Tirek: Because it makes me stronger each time.
Megatron: Get off me!
Starscream: I don't think so. [to Tirek] Tirek, it's time to show where your true loyalties lie.
Tirek: As you wish, my lord.