To determine the best spells for a Black Mage, we need to consider both the utility and effectiveness of each spell. Here’s a detailed breakdown of the most useful Black Magic spells:

### Level 1 Black Magic
1. **Sleep**
– **Effect**: Inflicts “sleep” status on all enemies, stopping them from attacking for a few rounds.
– **Usefulness**: Essential for controlling enemy movements and preventing attacks. It should be one of the first spells you purchase.

2. **Fire**
– **Effect**: Causes 10-40 Fire damage to one enemy.
– **Usefulness**: A basic elemental attack that is useful against most enemies. It’s a good starting point for elemental damage.

3. **Thunder**
– **Effect**: Causes 10-40 Thunder damage to one enemy.
– **Usefulness**: Similar to Fire, it provides an alternative elemental attack option. Choose either Fire or Thunder as they serve similar purposes.

4. **Focus**
– **Effect**: Reduces one enemy’s evade stat by 20.
– **Usefulness**: In some versions, this spell lowers evasion, which can be beneficial.

### Level 2 Black Magic
1. **Blizzard**
– **Effect**: Causes 30-120 Ice damage to all enemies.
– **Usefulness**: A powerful spell that hits all enemies on the screen, making it very effective against large groups.

2. **Hold**
– **Effect**: Stops one enemy from attacking.
– **Usefulness**: Useful for controlling a single enemy’s actions, especially against powerful foes.

3. **Thundara**
– **Effect**: Causes 30-120 Lightning damage to all enemies.
– **Usefulness**: Similar to Blizzard but with a different element, providing an alternative to Ice-based attacks.

4. **Focara**
– **Effect**: Reduces all enemies’ evade by 20.
– **Usefulness**: In some versions, it lowers evasion for all enemies, which can be beneficial.

### Level 3 Black Magic
1. **Ice2**
– **Effect**: Causes 40-160 Ice damage to all enemies.
– **Usefulness**: A more powerful version of Blizzard, making it effective against multiple enemies.

2. **Lit2**
– **Effect**: Causes 30-120 Lightning damage to all enemies.
– **Usefulness**: A more powerful version of Thundara, providing an alternative to Ice-based attacks.

3. **Hold2**
– **Effect**: Stops one enemy from attacking.
– **Usefulness**: Similar to Hold but with a higher success rate, making it more reliable for controlling enemy actions.

4. **Lok2**
– **Effect**: Reduces all enemies’ evade by 20.
– **Usefulness**: In some versions, it lowers evasion for all enemies, which can be beneficial.

### Level 4 Black Magic
1. **Blizzara**
– **Effect**: Causes 60-240 Ice damage to all enemies.
– **Usefulness**: A more powerful version of Blizzard, making it highly effective against multiple enemies.

2. **Haste**
– **Effect**: Doubles the number of hits your character can do per attack.
– **Usefulness**: Extremely useful in boss fights as it increases the character’s attack frequency, making them more effective.

3. **Sleepara**
– **Effect**: Inflicts “sleep” status on one enemy.
– **Usefulness**: More reliable than Level 1 Sleep and has a higher success rate, making it useful for controlling specific enemies.

### Additional Tips
– **Instant-Death Spells**: While some spells are powerful, they are not particularly useful due to their low success rates.
– **Elemental Balance**: Choose spells that balance elemental damage (Fire, Ice, Lightning) to ensure you have options against different types of enemies.
– **Status Ailments**: Spells like Sleep and Hold are crucial for controlling enemy movements and preventing attacks.

By focusing on these spells, you will have a well-rounded Black Mage capable of dealing elemental damage, controlling enemy movements, and enhancing your party’s physical power.