Byron, 23, recorded six goals and seven assists in 39 games with Springfield as a rookie in 2017-18.
Originally drafted by Pittsburgh in the sixth round in 2013, Byron played four seasons at the University of Maine from 2013-17.
Horton, 23, played four seasons at Harvard University before joining Springfield at the end of his senior season in 2017-18, appearing in nine games for the Thunderbirds.
Mangene, 29, reached the Calder Cup Finals with the Texas Stars in 2017-18, collecting seven goals and 19 assists for 26 points in 63 regular-season games and adding one goal and nine assists in 22 playoff outings.
Entering his seventh pro season out of the U. of Maine, Mangene has played 308 games in the AHL with Texas, Bridgeport and Adirondack, totaling 28 goals and 69 assists for 97 points.
Turgeon, 28, played 22 games for Springfield last season, picking up one goal and one assist.
In 92 AHL games over five pro seasons with Springfield, Portland and San Antonio, Turgeon has totaled three goals and three assists.
Driedger, 24, was a third-round pick by Ottawa in the 2012 NHL Draft. He was 2-5-0 in 10 AHL appearances with Belleville last season, with a 4.04 goals-against average and an .885 save percentage.
Driedger has played in 92 career AHL games with Belleville and Binghamton, going 38-39-6 with a 3.08 GAA, a .906 save percentage and two shutouts. He has also made three NHL appearances with Ottawa (0-1-0, 2.53, .889).