Regarding Watts, let's look at the monsters first, starting with Wattkiwi:
“Watt” monsters you control cannot be destroyed by battle while they are attacking.
Much like most battle protection effects, this is a Continuous Effect that you simply apply when the monster will be destroyed in battle. Note that the Watt monster must be attacking, it doesn't work in every type of battle.
Next, we have Watthopper:
Your opponent cannot select another face-up "Watt" monster on the field as an attack target, or target them with card effects.
Watthopper has two Continuous Effects. One prevents other Watt monsters from being selected as an attack target. If you control two or more Watthopper, no Watt monsters can be selected asn a attack target, and neither player can attack directly "over" them. The other effect prevents Watt monsters from being targeted by Card Effects. If they have already been targeted, and Watthopper is Special Summoned in response, Watthopper won't affect the targeting effect.
Then, we have Wattdragonfly:
If this card is destroyed by your opponent's card (either by battle or by card effect), you can Special Summon 1 "Watt" monster from your Deck.
Wattdragonfly has an Optional Trigger Effect that can't miss the timing. It can be activated even if Wattdragonfly is destroyed outside of the Field.
The last Watt monster in this set is Wattsquirrel:
This card can attack twice during each Battle Phase. If this card battles, negate the effects of the monster it battled after damage calculation (including in the Graveyard).
Squirrel's first effect is a Continuous Effect that allows it to attack twice during the Battle Phase. The second effect is a Mandatory Trigger Effect activated After Damage Calculation. It sets a Condition on the monster that negates its effects while on the Field and in the Graveyard, similar to the one set by Dark Ruler Ha Des.
We then have two Spell Cards, one being Wattcastle:
Any monster that attacks a "Watt" monster loses 1000 ATK after damage calculation.
Wattcastle has a Continuous Efffect that you apply After Damage Calculation, meaning that battle has already been carried out. Unlike Black Garden, this ATK reduction depends on Wattcastle remaining on the Field with its effect active.
And the other Spell Card being Wattjustment:
Equip only to a Level 3 or lower Thunder-Type monster. It gains 800 ATK and its effects are negated. Each time it inflicts Battle Damage to your opponent, draw 1 card.
Wattjustment has two Continuous Effects, one that gives an ATK increase, and one that negates the effects of the equipped monster that are applied on the Field. Additionally, it has a Mandatory Trigger-like effect that you activate after Damage Calculation when Battle Damage is inflicted.
The last Card for the Watt theme in this set is the Trap Card Wattkeeper:
Select 1 Level 4 or lower "Watt" monster in your Graveyard. Special Summon that monster from the Graveyard. Destroy it during the End Phase.
Wattkeeper targets a monster in your Graveyard. Then, it sets a Condition that will destroy the monster during the End Phase. If the Summoned monster stops being face-up, it's not destroyed.
Now, let's take a look at the Naturia Cards. Let's start with the first monster, Naturia Cherries:
If this card is sent from the field to the Graveyard by your opponent's card (including by battle, card effect, or by being destroyed), you can Special Summon up to 2 "Naturia Cherries" from your Deck in face-down Defense Position.
Cherries is similar to Wattdragonfly. It has an Optional Trigger Effect that can't miss the timing, but unlike dragonfly, it can only be activated if Cherries is sent from the Field to the Graveyard.
Then, we have Naturia Pumpkin:
When this card is Normal Summoned, if your opponent controls a monster, you can Special Summon 1 "Naturia" monster from your Hand.
Pumpkin has an Optional Trigger effect activated upon its successful Normal Summon. It can be negated by Pulling the Rug. It doesn't target, but you must have a Naturia Monster in your Hand at the time of the activation.
The last Naturia Monster is Naturia Stag Beetle:
Once per turn, during the Battle Step or Damage Step of this card's attack, when your opponent activates a card or effect, you can select 1 "Naturia" monster in your Graveyard. Special Summon that monster from the Graveyard.
Stag Beetle has an Optional Quick Effect. It's activated in a chain to the activation of a Card or the activation of a Card's effect, and it targets a monster in your Graveyard.
As for the Spell Cards, we have Barkion's Bark:
Activate only if you control a face-up "Naturia" monster. Your opponent cannot activate Trap Cards this turn.
Controlling a Naturia Monster is only an activation requirement. This Card's effect will resolve properly if that Naturia Monster is no longer face-up when this effect resolves. If you activate this Spell Card's effect via Diamond Dude, you don't need to control a Naturia Monster.
Then, we have Leodrake's Mane:
Select 1 face-up "Naturia" monster you control. Its ATK becomes 3000, and its effects are negated, until the End Phase.
Mane targets a monster you control. The ATK value becomes 3000, so it overrides any ATK modifiers currently being applied to the monster. Only the effects that are applied on the Field are negated.
The last Card for today is the only Trap Card for the Naturia theme in the set: Extrio's Fang:
Activate only if you control a face-up "Naturia" monster and have at least 1 card in your hand. Negate the activation of an opponent's Spell/Trap Card and destroy it. Then, send 1 card from your hand to the Graveyard.
Fang negates the activation of a Spell or Trap Card, so it can't negate the effects of an already-active S/T Card.
Well, that's all for Naturia and Watt monsters. Stay tuned for even more STBL! If you have any questions, feel free to drop me an e-mail at ness00[at]gmail[dot]com.