Alpha Steel




Alpha Neodymium

Alpha Promethium




Strongboxes are items that appear in SAS: Zombie Assault 4. They are the sole method of obtaining non-premium Weapons and Armor, unlike previous games where weapons were bought. You can find strongboxes in various locations throughout the game, but they are primarily located in secret rooms and can also be obtained by killing bosses. Multiple bosses do not give multiple strongboxes, and the amount of strongboxes obtained from a boss at the end of a mission is limited to one. Additionally, objects like vases in the VIP Mission can contain loot drops, including strongboxes. Killing zombies also has a small chance of dropping strongboxes, and collecting a Daily Reward may also award strongboxes. 

Tiers of Strongboxes

There are nine tiers of Strongboxes you can find. In order from lowest to highest tier, they are:

  1. Steel
  2. Titanium
  3. Molybdenum
  4. Iridium
  5. Neodymium
  6. Promethium
  7. Thulium
  8. Nantonium
  • Black: Black Strongboxes do not have a designated number for rating and need a key to be opened.


  • Each Strongbox opened contains exactly one weapon or armor piece.
  • The higher level the strongbox, the better items you'll get. However, it is strictly off chance, therefore there are still chance to unboxing great gear off low tier and undesirable gear off high tier, although there are less chance for those to happen
  • The higher level the strongbox, the more "flash" you'll see from collecting the box in a mission. Nantonium and Black strongboxes give off a lightning blast as well from the sprite which notifies the strongbox collected.
  • When obtaining an augment grade 8+ piece of gear from a strongbox, the interface will flash lightning twice in rapid succession and display the text "HIGH LEVEL GEAR!" in the upper-right-hand corner. However, this does not necessarily mean the gear is "good", as it could be bad gear with many augment slots and a high augment grade as well as unwanted pre-augments

Black Strongbox

A ninth Strongbox was added into the game in the February 3rd update of 2015, which can only be opened with a Selection 004 Key. You must be 25 or higher in order to open a Selection 004 strongbox. There is a small chance (5%) of obtaining a Selection 004 Key via a Nantonium Strongbox in Nightmare Mode, although they can also be obtained via rewards or be bought in the store for 20 Kreds/NK coins. Additionally, there is a chance of getting one as a reward for completing Events; if the player is in the Diamond tier, they'll have a 10% chance, Platinum a 5% chance, and Gold a 0.5% chance.

Selection 004 strongboxes contain a Selection 004 weapon/armor.

Also, unlike other strongboxes where players can just accumulate as many as they want, the player is only allowed to have a maximum of 5 Selection 004 strongboxes and any more must be discarded if they cannot be opened at the end of the mission in which they are collected.

Selection 004 strongboxes are not tier 9 strongboxes, and a Nantonium strongbox dropped when using High Roller will not turn into a Black strongbox. A Selection 004 strongbox can give any piece of black gear in the same drop range of nantonium strongbox.Meaning it is possible to get a black hornet at level 70 but will be at a lower grade than near it's drop range.

Related Achievements


  • The Steel, Black, and possibly Promethium, Thulium and Nantonium strongboxes are the only ones colored like the material they are made from.
    • Titanium strongboxes are green when they are actually silver-colored, Molybdenum strongboxes are blue when it is really gray, Iridium strongboxes are blue when it's actually silver-colored, Neodymium and Promethium strongboxes are purple when Neodymium is actually silver and Promethium's color is a silvery-white, although Neodymium in solution has a dark blue-purple color and in some forms of Promethium, it can have a blue-green glow, and Nantonium strongboxes are bright yellow, but its true color is unknown due to Nantonium being fictional.
    • All element-metals are silver/grey in color apart from gold and copper. The Strongboxes made from a pure element are all except Steel and Nantonium
    • There is, however, a possibility that Nantonium is naturally silver-white. An NK game called Magnetic Defense features a special item called "Nantonium Ball". It is a large, silver-white sphere. Apparently, Nantonium is very resilient, as the Nantonium Ball on Magnetic Defense can easily plow right through long lines of tanks.
  • Neodymium and Molybdenum are the only strongboxes to have their own special light color, as Thulium and Iridium share a greenish light, Nantonium and Titanium share yellow, and Promethium, Black and Steel share white, with Neodymium having purple lights and Molybdenum having light blue lights.
  • If you look on the atomic number in the periodic table of elements, the Iridium box should have the number 7 while the others (Neodymium, Promethium and Thulium) should have a tier less.
  • The mobile Version for SAS 4 does not have the same graphics for the strongboxes; instead they look more saturated in color with a different shape, and only have lights seen from the sides and not on top.
  • Selection 004 strongboxes have the Selection 004 logo on top.
  • The Christmas update features Christmas decorations that can be destroyed, which will always reveal a strongbox.
  • Non-boss zombies can drop a maximum of 10 strongboxes in a single mission
  • In PC version, it seems that lower level players will have a higher chance of getting a Selection 004 strongbox. As time goes on, the chance of finding one gets lower and lower
  • the 3x titanium strongboxes can be purchased in the in-game store gets more expensive for each level up starts from 25,000 sas4 creds at charecter level 1, increases by 2,000 each level.
  • When collecting multiple strongboxes at the same time, when the flash of the names appear, the highest tier strongbox will be the most visible. This is most notable in Nightmare Mode when a savage boss is killed without the loot spread. If you collect 2-3 boxes of the same tier due to this, the name of the strongbox will be bold text.


Steel Tiny Titanium Tiny Molybdenum Tiny Iridium Tiny Neodymium Tiny Promethium Tiny Thulium Tiny Nantonium Tiny Black Tiny
Smaller and more simple images.