As I am looking at the applicants so far and constructing relationships and roles, I am thinking I will likely touch base with players closer to challenge release to make SURE they are invested. Some of these concepts are so closely linked that if a player doesn't participate in the challenge, it dramatically reduces the point of related character concepts. So if you want to express interest, I can touch base with you again towards the end of May.

Also, you could have an existing character as a legacy (leaving a child, grandchild, or heir behind if you die, for example.) Such cases would just be a background detail in someone else's challenge, though, and not an integral plot device.