KPO

Equipment is one of the key requirements to growth each set has a different purpose:
PIRATE SET
Pirate set is specifically for siege

PROTECTOR SET
Protector set is for Defence

MARAUDERS SET
Marauders set is for ports

STRATEGIEST SET
Strategist set is for strategy games like tortuga/cannibal island and battle of the storm

CAPTAIN SET
Captain set is for hunting monsters/merchants/raid bosses/world boss and fleets

SCHOLAR SET
Scholar set is for research making it cheaper and quicker to complete research

ARCHITECT SET
Like scholar set this set is specifically to make building upgrade cheaper and quicker to complete