The item turns the bearer and their bullets into pure prime numbers. This means that each bullet and the Prime Primer bearer will only deal the most damage possible for their respective damage types, and all damage dealt will round up to the nearest integer. Enemy projectiles deal half damage against players under the effects of this.
When the player walks over it, it grants them a permanent boost to their health.
Prime Primer is not destroyed when used and can grant its benefit to the player multiple times.
It displays how much health it will grant in the tooltip and in its mouseover name.
The amount of health granted is shown as a percentage of your full health and is rounded down to the nearest 25 (e.g. if you have 99 health, walking over it gives you a +25% bonus or +3 health).
That is technically not a part of the Metroid series. It's neither a boss nor an item that Samus can acquire.
You can buy this item in Gungeon Proper.
The Gungeon Proper is the second chamber of The Gungeon and can be accessed by finding and entering the first big door. This is an iron prison, filled with nature and nature facsimiles, such as trees and foliage.
This nature is dangerous, as it will often result in fires erupting from holes in the floor.
In the depths of Gungeon lies a force that may hold the key to finding the Bullet That Can Kill The Past. Deep in a lost temple, a primordial substance known as Primer is said to exist.
This substance is a divine elixir, a wish-granter if you will. It is supposed to break barriers and confer power greater than any seen before.
The first step toward getting the Gun That Can Kill The Past is to simply be in the Gungeon.
Or rather, land on one of their many planets, but if you do that you’re probably gonna get shot for trespassing, so let’s just stick to teleportation or some other means of entry for now.
When first approached, the prime primers may appear to be no different.
However, it is important to note two things: (1) the prime primer has the power to spawn vermin of its own; though none as powerful as those it creates spawngrounds, and (2) its appearance allows the players to travel back in time to save an earlier version of themselves from imminent worm menace. Got that?
The Fighter's Companion is a craftable weapon for the second player character in Enter the Gungeon. The act of crafting it adds The Cultist to the player's team, since he/she cannot enter Gunships or dash (despite having special music) without it.
It is possible to use the Grappling Hook to steal items like the Prime Primer from display cases, but you must first acquire the item with one of your characters.
Once you do, go to any location where you can use the Grappling Hook, point it at the case holding the item, and throw it. Then, switch to another character that has not yet acquired that item and repeat.
When we first see the Gungeon, we witness a man named Bello running through the hallway attempting to steal the Gungeon. On his journey he is stopped by the bullets that come from the Gungeon and is killed.
Both of these events cause us to wonder; "What is this place?" and " What was the trigger that caused those sudden bullets to appear"?
Enter: the Prime Primer: a powerful artifact used by the Gungeon to reveal its true form and protect itself from thieves such as Bello.