Master of Orion II: Battle at Antares/Killing Space Monsters

Usually, the most attractive planets are guarded by space monsters.

There are six species of space monsters. Four of them have the serious problem of having just one weapon ready to deliver significant damage. This is what makes them rather unfortunate creatures that get wiped out quickly when standing in the way of the players expansion plans than a serious obstacle.

The key to eliminating foes with just one strong weapon is attacking with a bunch of small ships. Since the monster is just able to kill one ship per combat turn, the remaining ones can easily deliver the damage needed to destroy it without the need for expensive protective gear.

The most cost-effective approach is to take frigates with battle pods and load it with MIRVed missiles in racks of two rather than five. Eight of these will kill almost every minor monster and are cheaper to build than the colony ship needed for subsequent colonization. There's one exception, though. The Hydra needs at least 12 frigates or one "heavy armor" cruiser to soak up some damage because of the three independently targetable plasma weapons.

Tactical Approach to Space Monsters

 * Dragon:
 * Hydra: it has multiple plasma weapons that can decimate swarms of small ships.
 * Amoeba: it has an equalivant of plasma web, swarm the monster many missile frigates
 * Eel: the easiest monster to kill, although it has the equivalent of a lightning shield its attack only consist of a short-range shockwave, just fire volley after volley of MIRVed misiiles.

Antarans
Antarans will spawn unless they have been disabled via setup options. They will charge directly at a planet. A lone missile base (on each planet in the system) should be sufficient to defend your planets. Using ships against them is fairly counterproductive. Their ships will self destruct with enough damage.