A Tetrad Puzzle: Find The Key

I made this to test some ideas for a game I'm developing. Feedback would be appreciated.

What is the key?

• Would the enigmatic-puzzle tag be appropriate? Seems like it would. – Hugh Dec 24 '18 at 21:46
• This is a great puzzle. Visually very appealing and a nice level of difficult but doable! – Dr Xorile Dec 25 '18 at 1:25

Full Solution

Puzzle #1

Rules:

The number on a black triangle is the sum of its adjacents' numbers.

Key:

$$10 + 25 - 15 = 20$$

Puzzle #2

Rules:

We may rotate each pieces so that the corners inside the board are squares and circles. Then, look at the triangles (and its values), sum them to get the key.

D R R U U
U L R D D
R D R R L
U U L U D
L D U D U

Note: the holes are
S S C S
C S C C
C S S C
C C S C

Key:

$$-1 \times 7 - 2 \times 4 + 1 \times 8 + 2 \times 6 = 5$$

Puzzle #3 -- Thanks Dr Xorile for the help! ^^

Rules:

The word on the right is the antonym of the word on the left.

UP DOWN
B(E)GIN END
NIC(E) (N)AUGHTY
HEA(V)EL H(E)LL
VIC(T)ORY DEFEAT
PUB(L)IC PR(I)VATE
S(W)IM SI(N)K

Key:

TWELVE - NINE = $$3$$

Puzzle #4

Rules:

For the numbers, sum the value of black circles. The value is the position from the right side.

@: inverse (black to white, white to black) all circles.
#: inverse first half of circles.
%: inverse last half of circles.
$: add 2 white circles in the end. Now we must identify the symbols replacing X, Y, and Z. Answer: As the inverses are commutative, \$X% will be the same as \$%X, this allows us to identify each letters easier. X = @ Y = % Z = # XY\$X\$ZY = @%\$@\\$#% = WWBBWWBB

Key:

$$6+5+2+1 = 14$$

Final Puzzle

For each colors, we may "mix" the keys from previous puzzles.
Then the numbers can be converted to letters (of 26).

Yellow: 3 = C
Blue: 20 = T
Pink: Red + White = 5 + 14 = S
Purple + 10: Red + Blue + 10 = 5 + 20 + 10 = 35 (9) = I
Red: 5 = E
Green: Blue + Yellow = 20 + 3 = W
Orange: Red + Yellow = 5 + 3 = 8 = H

Anagram it, we will get WITCHES, as their words have power.

I really enjoy solving this puzzle, great work! :D

• Nice work! CHOYVP CEVINGR and FJVZ FVAX (ROT13) – Dr Xorile Dec 24 '18 at 22:49
• Last one is URNIRA URYY – Dr Xorile Dec 24 '18 at 22:55
• Which leaves gjryir zvahf avar = guerr – Dr Xorile Dec 24 '18 at 22:58
• Yep that's the key, thanks! :D -- now only the last one is unsolved – athin Dec 24 '18 at 23:00
• @NigelMNZ It's fun and well-made, I'm impressed. Thanks and good luck for (+ looking forward to) the game! ^^ – athin Dec 24 '18 at 23:35