SAS Zombie Assault Wiki

Strongboxes are loot boxes that appear in SAS: Zombie Assault 4. They are the sole method of obtaining non-premium Weapons and Armor normally (Certain Armor available in SAS4 Mobile/Steam using real money), 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 - although savage bosses on Nightmare Mode will drop two to three. On mobile, during nightmare mode Savage Devastators can drop up to 4 strongboxes and Savage Necrosises can drop up to 5.

Additionally, objects like vases in the VIP Mission can contain loot drops, of which can occasionally included strongboxes. Killing zombies also has a small chance of dropping strongboxes, and collecting a Daily Reward will also award strongboxes depending on the daily reward the selected character you're using is up to. 

Tiers of Strongboxes

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

  1. Steel (45% drop rate on mobile, 35% for flash)
  2. Titanium (20% drop rate on mobile, 24% for flash)
  3. Molybdenum (15% drop rate on mobile, 15% for flash)
  4. Iridium (10% drop rate on mobile, 10% for flash)
  5. Neodymium (5.5% drop rate on mobile, 6.5% for flash)
  6. Promethium (3.1% drop rate on mobile, 3% for flash)
  7. Thulium (1% drop rate on mobile, 1.5% for flash)
  8. Nantonium (0.4% drop rate on mobile, 5% for flash)
  • Black: [BLACK] Version Strongboxes do not have a designated number for rating and need a key to be opened. They sometimes replace the Nantonium strongbox, as both of these types share the same properties. Also, if a Thulium strongbox is upgraded to a Nantonium through High Roller, it does NOT have the chance to be transformed into a [BLACK] Version Strongbox, nor does it have the chance to grant you a Black Key from a Nightmarish boss, making this boost nearly useless for the endgame.


  • Each Strongbox opened contains exactly one weapon or armor piece.
  • The higher level the strongbox, the better items you'll get, and the higher tier weapons you can obtain. However, you can still get undesirable weapons.
  • Ever since the Nantonium Strongbox nerf in September 2015 on Flash, the range of weapons can be that of a steel strongbox to the thulium, making the Thulium strongbox technically better for acquiring the best gear on that version.
  • 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 [BLACK] Version Key. You must be level 25 or higher in order to open or scrap a [BLACK] Version strongbox. There is a small chance (5%) of obtaining a [BLACK] Version Key via a Nantonium Strongbox in Nightmare Mode, although they can also be obtained via rewards or be bought in the store in packs, for around 20 Dollars. 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.

[BLACK] Version strongboxes are restricted to only containing [BLACK] Version 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 [BLACK] Version strongboxes and any more must be discarded if they cannot be opened at the end of the mission in which they are collected. However this function can be overridden if additional [BLACK] Version strongboxes are obtained via rewards and being bought from the store, these [BLACK] Version strongboxes will remain in you collection until they are either opened or scrapped. It is of course better to scrap at least one [BLACK] Version strongbox you have so that a sixth collected in-game can be kept.

[BLACK] Version strongboxes are not tier 9 strongboxes, and a Nantonium strongbox dropped when using High Roller will not convert into a [BLACK] Version strongbox. A [BLACK] Version strongbox can give any piece of [BLACK] Version gear in the same drop range of nantonium strongbox, meaning it is possible to get a [BLACK] Version hornet at level 70, however doing so will likely sacrifice the weapons grade and it will be much lower than it would be if dropped at its normal range.

Related Achievements


  • The Steel, [BLACK] Version, 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.
    • The Prometheum Strongbox is the only Strongbox currently in-game to not have the Caduceus-looking logo on it.
  • 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.
  • [BLACK] Version strongboxes have the [BLACK] Version logo on top.
  • The Christmas update features Christmas decorations that can be destroyed, which will always reveal a strongbox. Keep an eye out for Christmas trees and red barbels around the maps you play, there are several locations that they will spawn in on each map, however it is possible for none to spawn. These Christmas ornaments will only spawn in on standard and Nightmare game modes, they will not spawn in contract missions nor events.
  • Non-boss zombies can drop a maximum of 10 strongboxes in a single mission (excluding Nightmare Mode)
  • In PC version, it seems that lower level players will have a higher chance of getting a [BLACK] Version strongbox. As time goes on, the chance of finding one gets lower and lower
  • Four Titanium strongboxes can be purchased in the in-game store for a hefty price which gets more expensive for each level the character increase. This starts from 25,000 sas4 creds at character level 1 and increases by 2,000 each level. It actually says you buy three Titanium strongboxes, and this was actually true for some time, but an update to the game messed with the code and you now get four.
  • 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.
  • A Black Box is also an alcoholic brand of drinks, more notible for their wines, but also for their wiskey, vodka and tequila.
  • It is easy to mistake a Titanium strongbox with a Nantonium and vice versa on the PC version due to the similarity of the strongboxes image, especially with graphics set to low. Obviously this can be fixed by simply moving over the strongbox to find out what actually dropped.
  • High Roller will disable Steel Strongboxes from dropping in-game, however it is still possible to obtain Steel strongboxes if your character levels up after the game - many players get confused with this, due to character levelling up strongboxes being fixed. If any strongbox including Steel is collected before purchasing High Rolled when already in-game, the box(es) will not increase the tier nor will have the buff to the equipment inside.
  • A game named Tower Defense Simulator on the platform known as Roblox copied this crate design to use for their "Golden Skincrate"


Flash strongbox icons

Mobile strongbox icons

Mobile Strongboxes and black boxes

In-game strongboxes (Flash)

In-game strongboxes (Mobile)