Here is a concise summary of the text:
**Subject:** Spirit Fox Pet in Clash of Clans (Town Hall 16)
**Key Points:**
1. **Availability:** Upgradable Pet House to Level 9 (21M Elixir, 15-day upgrade) at Town Hall 16.
2. **Special Ability:** "Spirit Walk" - periodically turns the pet and its assigned hero invisible for 4 seconds.
3. **Stats:** Comparable to Frosty, with slightly less HP but more damage per second.
4. **Strategy:**
* Recommended for Barbarian King and Royal Champion due to their melee range.
* Avoid using with Archer Queen and Grand Warden (longer range, making the pet vulnerable).
5. **Tips:**
* Utilize with Royal Champion for a strong combo against defenses.
* Can be used with invisibility spells for extended stealth periods.
6. **Upgrades:** 10 levels, costing over 2M Dark Elixir; key upgrades at levels 5 and 10 for increased invisibility duration.
Here are the key facts extracted from the text, keeping each fact as a short sentence and numbered for reference:
1. **New Pet Release**: A new pet, the Spirit Fox, is available at Town Hall 16 in Clash of Clans.
2. **Pet House Upgrade**: Upgrading the Pet House to Level 9 (required for the Spirit Fox) costs 21 million Elixir and takes 15 days.
3. **Spirit Fox Unlock**: The Level 1 Spirit Fox is unlocked after upgrading the Pet House to Level 9.
4. **Special Ability**: The Spirit Fox's special ability is "Spirit Walk", which periodically turns itself and its assigned hero invisible.
5. **Invisibility Duration**: The Spirit Fox and its hero are invisible for 4 seconds, then visible for 4 seconds, repeating as long as the pet is alive.
6. **Vulnerability**: The Spirit Fox is vulnerable to the new Ricochet Cannon, like other pets.
7. **Upgrade Costs**: Upgrading the Spirit Fox through its 10 levels costs over 2 million Dark Elixir.
8. **Key Upgrades**:
* Level 5: +5 seconds of invisibility.
* Level 10: Additional 0.5 seconds of invisibility, totaling 4.5 seconds.
9. **Stats at Max Level**: The Spirit Fox's stats are comparable to Frosty's, with slightly fewer hit points but more damage per second.
10. **Unique Aspect**: Unlike some pets, the Spirit Fox does not transfer to another hero if its assigned hero goes down.
11. **Heroes Compatibility**:
* Recommended: Barbarian King and Royal Champion.
* Not Recommended: Archer Queen and Grand Warden (due to their greater range).
12. **Additional Effect**: The Spirit Fox slows down defenses it attacks, similar to Frosty's frost mites.