Phillips initially joined Palace in January 2022 from Drogheda United and went on to make his professional debut for the club at the start of the 2022/23 season against Oxford United in the League Cup.
He has had loan spells at Shrewsbury Town, where he won the club’s Young Player of the Year award, Wycombe Wanderers and most recently for Aberdeen in the Scottish Premiership.
The midfielder now returns to the Scottish Premiership to be a part of Stephen Robinson’s side, as they look to build on their fifth place finish last season.
Everyone at the club wishes Killian well on his loan spell.