Certainly! Here's a test case generator for the given problem "The Humans Braving the Invaders":

```python
import random

def generate_query(L):
    query_type = random.randint(0, 4)
    if query_type == 0:
        return "0"
    elif query_type == 1:
        d = random.randint(1, 10**9)
        return f"1 {d}"
    elif query_type == 2:
        k = random.randint(1, 10**9)
        return f"2 {k}"
    elif query_type == 3:
        x = random.randint(0, L)
        r = random.randint(0, 10**9)
        return f"3 {x} {r}"
    elif query_type == 4:
        k = random.randint(1, 10**9)
        return f"4 {k}"

def tcgen():
    datasets = []
    
    num_datasets = random.randint(1, 3)
    for _ in range(num_datasets):
        Q = random.randint(1, 100000)
        L = random.randint(1, 10**9)
        
        queries = []
        for _ in range(Q):
            queries.append(generate_query(L))
        
        datasets.append((Q, L, queries))
    
    return datasets

def format_dataset(dataset):
    Q, L, queries = dataset
    result = [f"{Q} {L}"] + queries
    return "\n".join(result)

def main():
    random.seed(42)  # For reproducibility
    test_cases = tcgen()
    for dataset in test_cases:
        print(format_dataset(dataset))
        print("end")
    print("0 0")

if __name__ == "__main__":
    main()
```

### Explanation:

1. **generate_query(L)**: Generates a single query based on the problem constraints.
2. **tcgen()**: Generates multiple datasets, each with its own set of queries.
3. **format_dataset(dataset)**: Formats a dataset into the required input format for the problem.
4. **main()**: Generates the test cases, prints them, and adds the required "end" and "0 0" at the end.

### Usage:

When you run the `main()` function, it will generate random test cases for the problem and print them out in the required format. It ensures that the constraints are respected for each query and dataset.

Note that I've added a seed for random to make the test case generation reproducible. You can remove or modify the seed for different results each time you run the generator.