How to use the Guardian of Alola Z-move in Pokemon Sun/Moon?

[Marc]

Tapu Koko has two fairy type Z moves :

• Twinkle Tackle
  
• Guardian of Alola

I'm guessing Fairium Z activates Twinkle Tackle but what exactly activates Guardian of Alola? Is it the Tapunium Z item? In its description it says it upgrades nature's madness for an exclusive Z move.

Also, what does Guardian of Alola do exactly?

According to Serebii, it has 1 attack point and it says :

The user, the Land Spirit Pokémon, obtains Alola's energy using its Z-Power and attacks the target with full force. This reduces the target's HP greatly.

How is the damage calculated?

Thanks!

 

[Mr. Kream]

Tapunoium Z and Nature's Madness activate Guardian of Alola, and it does 75% of the target's current health. It can be very useful in targeting mon that can't heal consistently, like Groudon.

 

[Marc]

Tapunoium Z and Nature's Madness activate Guardian of Alola, and it does 75% of the target's current health. It can be very useful in targeting mon that can't heal consistently, like Groudon.

I see, thanks!

 

[Mr. Kream]

http://replay.pokemonshowdown.com/gen7ubers-568113909

It's Ubers, but it's a good example, Turn 34. Also, if you launch off Guardian of Alola into Protect, it will only do 1 damage and ends up being a turn entirely wasted, so time it right.