This dream is quite vivid and packed with symbolism, which can make it both intriguing and unsettling. Let's break it down to explore its potential meanings.

1. Combat and Survival: The dream begins in a high-stakes firefight, indicating a sense of conflict or struggle in your waking life. This could relate to personal challenges, emotional battles, or external pressures where you feel you must "fight" to survive or succeed.
2. The Hosts as Otherness: The creatures resembling ET might symbolize feelings of alienation or encounters with the unknown. They could represent aspects of yourself or situations that feel foreign or unfamiliar. Your initial readiness to attack them suggests a defensive stance towards what you do not understand or fear.
3. The Act of Killing: The moment you realize the host did not fight back and your subsequent remorse indicates a deeper conflict within you. It may suggest feelings of guilt or regret over actions taken in your life, particularly towards those who may not have posed a real threat.
4. The Substance: The milky, filmy substance that connects the hosts could symbolize interconnectedness or the consequences of your actions. It may reflect your awareness of how your choices affect others, particularly in a relationship context.
5. Transformation and Creation: The transformation of the substance into what appears to be a fetus highlights themes of creation, potential, and perhaps the birth of new ideas or aspects of yourself. This could signify a desire for growth, change, or a new beginning in your life.
6. Emotional Processing: Your reaction of kneeling in reverence suggests a desire to process, understand, or honor the impact of your actions, both on yourself and on others. This could be leading you to reflect on your relationships and how your decisions resonate within them.

In summary, this dream may be a reflection of your internal struggles with conflict, guilt, and the desire for connection and understanding. It might be helpful to take some time to reflect on any current conflicts in your life and how they could be influencing your emotions and decisions. Consider journaling about your feelings or discussing them with someone you trust for further clarity.