Sure, I can help you write a test case generator for this problem. Here is a Python function that generates random test cases for the problem "Indian Puzzle":

```python
import random

def generate_grid(H, W):
    grid = []
    for _ in range(H):
        row = []
        for _ in range(W):
            cell = random.choice(['.', '#', str(random.randint(0, 9)), random.choice(['+', '-', '*', '/', '='])])
            row.append(cell)
        grid.append(''.join(row))
    return grid

def generate_characters(n):
    chars = []
    for _ in range(n):
        char = random.choice([str(random.randint(0, 9)), random.choice(['+', '-', '*', '/'])])
        chars.append(char)
    return chars

def tcgen():
    datasets = []
    
    while True:
        H = random.randint(1, 10)
        W = random.randint(1, 10)
        grid = generate_grid(H, W)
        n = random.randint(1, 10)
        characters = generate_characters(n)
        
        dataset = f"{H} {W}\n" + '\n'.join(grid) + f"\n{n}\n" + ' '.join(characters)
        datasets.append(dataset)
        
        if random.random() < 0.1:  # 10% chance to stop adding more datasets
            break
    
    datasets.append("0 0")
    
    return '\n'.join(datasets)

# Example usage:
print(tcgen())
```

### Explanation:

1. **Function `generate_grid(H, W)`**: This function generates a random grid of dimensions `H` x `W`. Each cell can be a blank (`.`), a black cell (`#`), a number (`0-9`), or an operator (`+`, `-`, `*`, `/`, `=`).

2. **Function `generate_characters(n)`**: This function generates a list of `n` random characters which can be numbers (`0-9`) or operators (`+`, `-`, `*`, `/`).

3. **Function `tcgen()`**: This function generates multiple datasets:
    - It first decides the dimensions `H` and `W`.
    - It then generates a grid of these dimensions using the `generate_grid` function.
    - It also decides a number `n` of characters and generates these characters using the `generate_characters` function.
    - It combines the grid and characters into a single dataset string.
    - It keeps adding datasets into a list until a random stopping condition is met (10% chance to stop each iteration).
    - Finally, it appends the end-of-input marker (`"0 0"`) and returns the complete set of datasets as a single string.

When you run `tcgen()`, it will print a randomly generated input set adhering to the problem's constraints.