Upon starting, you'll have Arkantos, a few Murmillos, and an Oracle Scout. Immediately queue up additional Murmillos from your Barracks. Position your starting Murmillos near the docks, anticipating the Kraken's attacks. Use your Oracle Scout to explore the immediate vicinity, revealing nearby resource nodes and any early enemy patrols. The Kraken will periodically emerge from the water to attack your docks. Focus all your military units on the Kraken when it appears. Don't let it destroy your docks, as this will fail the mission. Keep your Murmillos healthy by micro-managing them, pulling back damaged units if necessary. If you have any healing God Powers available (though unlikely this early), save them for critical moments. The key is to maintain a steady stream of Murmillos to counter the Kraken's damage output.
Ensure your Oracle Scout is constantly moving and exploring, as early map knowledge is invaluable. You'll also want to gather resources to continue training units. Prioritize Food and Wood initially. Don't overextend your forces; keep them concentrated around the docks until the objective is complete. The initial defense phase is a test of your ability to manage unit production and engage a powerful enemy effectively.