I wanted to try Shevy's new key but unfortunately all of the ice dolls are bad at this event because the Disconnection debuff. Except for Makiatto, who is actually excellent at this event.

For anons struggling this event and who not have wheelchairs to carry them, try using Makiatto if you have her at V1. I know many day 1 players here do.

The Heroic Mode Disconnection debuff makes your dolls deal no damage until the've made one single target attack each turn. Because V1 Makiatto attacks twice with her S1, the 2nd attack does full damage so she can one shot most enemies with it. Then, she does two interceptions that will also deal full damage. She ends up killing 3 enemies every turn if she is decently built and you make use of her interception.