Forward Danny Rowe joins after finishing last season with the now-defunct Walton Casuals.
The 25-year-old had joined the Stags in July 2021 from then-Isthmian Premier side Leatherhead.
He had been with the Tanners since February 2020 after joining from Vanarama National League South side Oxford City.
He had been frustrated with injuries and, despite being back to full fitness, found starting opportunities limited with Oxford.
His highlight was a first-half hat-trick in the Hoops` 6-2 win at Chelmsford City in November 2019.
He started his career with Leicester City and progressed through the under-18 and under-23 ranks.
He left the King Power Stadium to join Queens Park Rangers in January 2017 and was a regular in the R`s under-23 side.
After being released by Rangers, he joined Braintree Town in August 2018 before switching to National League North side Boston United the following November.
He returned to the Iron in January 2019 and then made the switch to City in the summer of 2019.
Also joining the Geordies is 18-year-old centre-back Jeremy Stewart.
Stewart has returned home to London having been released by Championship side Huddersfield Town in the summer.
Stewart joined up with Huddersfield’s under-17s group ahead of the 2020/21 season.
He progressed to the Terriers` under-19 side but wasn’t kept on for 2022/23.