Step3.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Step3 : MonoBehaviour
{

    // Regenerate creature every 30 seconds
    public bool auto = true;
    public float autoGenerateTime = 30;

    private GameObject parent;
    private GameObject left;
    private GameObject right;

    public List<GameObject> shapes;
    private Object[] materials;

    // Start is called before the first frame update
    void Start()
    {
        // regenerate creature
        if (auto)
        {
            InvokeRepeating("GenerateShapes", 0.0f, autoGenerateTime);
        }

        // load materials from Resources folder
        materials = Resources.LoadAll("Materials", typeof(Material));
    }

    void GenerateShapes()
    {
        // clear for new creature
        Destroy(parent);

        // choose random material
        Material material = (Material)materials[Random.Range(0, materials.Length)];

        // Skeleton 
        parent = new GameObject();
        left = new GameObject();
        right = new GameObject();

        parent.name = "Creature (Parent)";
        left.name = "left";
        right.name = "right";

        // set parent
        left.transform.parent = parent.transform;
        right.transform.parent = parent.transform;

        // loop to generate creature parts
        for (int i = 0; i < 10; i++)
        {
            int randShape = Random.Range(0, shapes.Count);

            GameObject go = Instantiate(shapes[randShape], new Vector3(Random.Range(0.35f, 3.0f), Random.Range(-1.0f, 3.0f), Random.Range(-1.0f, 3.0f)), Quaternion.identity);
            GameObject go2 = Instantiate(shapes[randShape], new Vector3(-go.transform.position.x, go.transform.position.y, go.transform.position.z), Quaternion.identity);

            // add color
            go.GetComponent<Renderer>().material = material;
            go2.GetComponent<Renderer>().material = material;

            go.transform.parent = left.transform;
            go2.transform.parent = right.transform;

            go.SetActive(true);
            go2.SetActive(true);
            
        }

    }

    // Update is called once per frame
    void Update()
    {

    }
}