Xbox One Preview Program members will get a chance to take part in a weekend-long closed beta for Motiga's upcoming shooter MOBA Gigantic. Microsoft has begun alerting Preview members that they are invited, noting that they simply have to visit the Beta Games and Apps section of the Preview Dashboard to redeem their code. From Microsoft:

Go Gigantic this weekend and play in the Gigantic Closed Beta, an upcoming shooter MOBA! To participate, launch the Xbox Preview Dashboard app and visit Beta Games and Apps to redeem your code. There are a limited number of codes, so don't delay!

For those who have already participated in a previous closed beta, you should already have access, so you won't have to redeem a new invite code via the process described above.