Striker joins Peterborough Sports for a second time and could make his debut at Chester on Saturday
He was part of a Darlington squad that looked nailed on for a play-off place last season until a late collapse saw them finish 10th.
The Quakers have struggled badly this term and are currently the only team below Sports in the National League North table.
Felix scored four goals in 56 appearances for Darlington. He started three games this season without scoring.
Felix could make his debut for Sports in a tough league game at Chester on Saturday.