The Fifth Base
The Fifth Base (formerly Fifth Base) is a unique rule to Blaseball that places an additional base on the field which players are required to run through before reaching home plate.
When the The Fifth Base Modification is applied, lineup players must run five bases instead of the usual four. This results in the ability for players to hit a "Quadruple" (a hit allowing players to advance four bases) as well as a "Pentaslam" (A home run with a runner on all four bases, scoring five runs total).
The first Pentaslam was hit on Season 10, Day 7 by Simon Haley of the Charleston Shoe Thieves during a game against the Philly Pies. It was awarded with the discovery of The 4-Blood Blagonball.
On the Season β7 Election Ballot, Fifth Base was offered to the league as a decree. At that time, Fifth Base was not selected, with the vote going to Bless Off instead.
In the Season β9 Election Ballot, Fifth Base Bubble was offered to the league as a blessing, promising to protect the subleague of the team that won the blessing. The Baltimore Crabs won the blessing, protecting Wild High, but exposing Mild High, Mild Low, and Wild Low to Fifth Base for the duration of Season β10.
The Fifth Base would later appear in the Expansion Era as a part of the Super Roamin' Fifth Base Blessing in the Season β19 election. The Fifth Base could be placed by players, and in doing so the Ballpark that the Base was placed in would gain the Fifth Base modification until the Base was stolen once again.
When Fifth Base is active, an extra plate is placed behind third plate, opposite from home plate. The Commissioner tweeted a diagram of the path players must run to reach home plate. Players run through first, second, and third plates as normal, then they run away from home plate to the fourth plate, before running back past third to reach home.
The Blaseball simulation appears to account for the extra distance running to the fourth plate, with fourth plate being easier to steal, and home plate being harder to steal.
The existence of a Sixth Base has been theorized but only observed in extremely infrequent and unstable conditions. It is not known whether a sixth base can remain stable for macroscopic lengths of time.
Even rarer is the sighting of a Seventh Base, which has only been seen when Quack Enjoyable refused to go home in for unknown reasons.