Once a World Blessing is used, the entire server gets an additional 25% EXP for 1 hour.
To see if a World Blessing is in use, look in the top-left corner.
World Blessings can be bought from the Credit Shop. It costs 300 credits (270 after discount from Gold Membership). They are also one of the possible prizes from both Mystery Box and Item Bomb, and can also be found inside Easter Eggs and Presents.
Using a World Blessing awards Philantropist Points equal to the amount of players online. The max is capped out at 500.