So on characters that say they can "Pray" and add 1 to their die roll, i have a few questions.

Can they pray any number of times during their turn or is it a limit?

Can they pray for die rolls they make for a card they encounter..IE Regeneration on a troll for instance?

"Prayer" is only on certain spaces; Chapel, Graveyard, and Temple. There are some cards as well (Shrine being the only one to come to mind atm). Usually the instructions say "Pray by rolling 1 die" (2 in the Temple).

So, there would be a limit (1 roll per encounter), and only in specific instances.

Mr Maple Syrup is correct. Frostmarch added one or two Adventure cards that have the "pray" keyword in them (one for sure, might be two).