The Ruin is a boss zombie exclusive to SAS Zombie Assault Tower Defense. It has the appearance of a gigantic flaming demon and is the toughest enemy in the game. Not surprisingly, it can withstand most defenses, demolish them in turn very quickly, and is extremely durable, to the point where not even a Necro Nuke can kill it in 1 shot.
Despite the fact that the zombie is not named in the game, it has been referred to by the developers as "Ruin". However, internally, it is simply called 'Boss'.
The Ruin will increasingly spawn in Freeplay mode after killing it in the final required wave of whichever map the player is playing on. When killed, the Ruin lets out a defeated growl.
- The Ruin has a ranged attack that can easily dispatch towers and SAS Soldiers. Integrated Barbwire can be very helpful, weakening it before it gets up close to punch them. It can even reach soldiers and turrets that are placed on high ground, albeit less often.
- The Ruin's high health and damage can easily bypass minor to moderate defenses in mere seconds; use everything, including Necro Nukes, if the situation becomes dire.
- The Ruin will kill all of the civilians when it reaches the exit, so killing the Ruin is mandatory if the player wants to win.
- A single MAD Sniper SAS can kill a Ruin with the help of only 1 cryo grenade.
- Anti Tank Titanium barricades can hold off a Ruin for a while (about 7 hits). Also be sure to have high powered units to take it out while attacking the barricades, or else just sell them to improve other units.
- After a few waves, the Ruin's health will begin to increase, so make sure that the player's forces attack it as much as it can until the Ruin is dead.
- The Wicker from SAS: Zombie Assault 4 is very much like the Ruin; it is a large zombie, around the size of a Devastator, has horns, is dark-colored, and on fire—just like the Ruin. Notably, it can throw balls of fire as an attack. It also explodes in a massive fireball when killed. The Devastator (in SAS 4) and Wicker both appear to have elements of the Ruin in them.
- The Ruin also has some clear reference to the Balrog from The Lord of the Rings. They both have horns, and are on fire, but most of all they look similar in general with a muscular physique.