[3] After being a student of Fight Factory Pro Wrestling for one year, Cusack made her debut in 2015 adopting the ring name Valkyrie Cain (after the protagonist of the Skulduggery Pleasant book series by Derek Landy).

[8] In February 2020, Valkyrie toured with WWE's US-based NXT brand for the first time, wrestling on two house shows in Florida.

[14] On 23 May, she also defeated Cora Jade to advance to the final, facing Tiffany Stratton at NXT Battleground, where she ultimately lost.

[17] Earlier in the show, Valkyria noted she was inspired by Lynch's NXT debut and remarked on the elder's impact on Irish wrestling.

[20][21] After their match, Lola Vice tried to cash in her Breakout Tournament contract, only to be stopped by Tatum Paxley, who was obsessed with Valkyria since December 2023.

[32] On the 6 May episode of Raw, Valkyria made her on-screen debut saving Women's World Champion Becky Lynch from a beatdown by Damage CTRL's Dakota Kai, Iyo Sky and Kairi Sane, and at the same time defeated Kai in the first round match of the Queen of the Ring tournament in her main roster in-ring debut.

[33] She proceeded to defeat Zoey Stark in the quarter-finals and Sky in the semi-finals but lost to Nia Jax in the finals at King and Queen of the Ring, marking her first loss on the main roster.

[41] Starting in December 2024, Valkyria entered a tournament for the inaugural Women's Intercontinental Championship, where she defeated Ivy Nile and Zelina Vega in the first round,[42] and Iyo Sky in the semifinals.

On the January 13, 2025 episode of Raw, Valkyria defeated Dakota Kai in the finals of the tournament to become the inaugural champion.