Arachnian Exterminator Edit
The Arachnian Exterminator is formed out of a Mantian Queen and can transform itself into an Arachnian Demolisher. It has a relatively slow rate of fire that makes it unsuitable as a frontline unit. Instead, it can be deployed either as field artillery against enemy units lacking chemical armor or as heavy artillery against enemy structures, in which regard it clearly outclasses the Hermipterian Grenadier.
This unit, with its specially mutated internal secretion system emits a chemically unique and extremely concentrated caustic substance, which is actually able to melt the defensive coating of hostile structures.
Arachnian Demolisher Edit
The Arachnian Demolisher is formed out of an Arachnian Exterminator. While it's even more slow-firing than its predecessor, the Demolisher is one of only two Alien units that inflict armor-piercing damage. Just like the Exterminator, the Demolisher is unsuitable as a frontline unit; indeed, its best use is the long-range shelling of enemy bases. Since it has a limited usefulness against enemy units and does the same amount of damage the Exterminator does with a lower rate of fire, most of the time the water spent to transform an Exterminator is better spent elsewhere.
The Builders decided to introduce an additional nucleotid to the Arachnian Exterminator DNA chain. This alteration enabled caustic substances to mutate into enormously tough shells - a hugely effective unit with awesome capabilities.