You chose to be Icy's helper.
Yeah, it was your choice. She didn't force you to. You just took it on all by yourself.
Then, the faithful day came.
Your first mission.
"Miss Icy?"
Icy: "Yes?"
"Isn't it time for my first mission?"
Icy: "Oh yes. Indeed it is."
"What do you want me to do?"
Icy: "I need you to steal this from the Winx."
She showed you an image of a grimoire. This specific grimoire, however is one that took his father years to keep all the powerful spells intact without fail.
Realizing what the grimoire was, you knew you had to do this. You needed to get that cherished object back.
Once nighttime hit, you snuck to Alfea and right into the room of the Winx. You knew this would be risky, but you had to do it.
After sneaking around the room, you found the grimoire. Slowly but surely, you grabbed the grimoire and bolted out of the room.
You returned to the Trix's hideout with the grimoire in your hand.
"Here you go, Miss," you said to your master.
Icy: "Congratulations. You got exactly what my sisters and I wanted."
"Actually, it's my father's, bu--"
Icy: "Excuse me?"
"You see, that belonged to my father, and he wanted to keep any and all spells in one object out of convenience."
Icy: "I didn't know that."
"Yeah, its a thing that I lost for a loooooooooooooooooong time, and I've been wanting it back."
Icy: "I didn't know that."
"You can have it if you want it badly."
Icy: "No."
"No?"
Icy: "I know you cherish your father's creations."
"Yeah..."
Icy: "I'll let you keep it, as long as you do my sisters and I a favor."
"Okay, shoot."
Icy: "You will help us in taking over Alfea."
"Okay. Not a problem."