Mason made a 3-pointer that gave Niagara a 60-56 lead and sparked a 14-5 run during which Mason hit two more to put the Purple Eagles up 70-61 with 2:59 left.
Niagara went ahead 47-40 with 14:31 left to play, but Marist took its first lead of the second half at 51-50 on Khallid Hart's layup with 9:47 to go.
The teams exchanged the lead three times and tied twice before Marcus Ware's free throw gave Niagara (6-15, 3-7 Metro Atlantic Athletic Conference) the lead for good at 57-56.
Chavaughn Lewis had 25 points to lead Marist (6-13, 3-6) which shot 28 of 52 from the floor and out-rebounded the Eagles 31-27, but couldn't overcome 16 turnovers.
Mike Smith scored 24 points, Gabe Stefanini added 19 and Columbia held off Brown for an 89-82 win on Friday night.
Last year, Arizona traveled to Eugene to face Oregon in a top-15 Pac-12 showdown with national ranking implications.
FBI wiretaps intercepted multiple conversations between Arizona coach Sean Miller and Christian Dawkins, in which Miller discussed a $100,000 payment to ensure star freshman Deandre Ayton signed with the Wildcats, sources told ESPN.