#2
chords that have a diminished fifth in them

diminished chord/triad: 1 b3 b5
just a minor third on top of a minor third

diminished 7th chord: 1 b3 b5 bb7 (thats a diminished seventh, which is enharomonic but not identical to a major sixth)
this one repeats itself as an inversion every 3 frets (as its also just continuously stacked minor thirds)

half diminished 7th chord (m7b5): 1 b3 b5 b7
(this chord is built off the locrian mode)
#3
Minor chords with a flatted fifth tone. Like for example:
E minor is E-G-B
E diminished is E-G-Bb (move the B note down one fret to B flat)
Then there's this band called Slice The Cake...

Bunch of faggots putting random riffs together and calling it "progressive" deathcore.
Stupid name.
Probably picked "for teh lulz"

Mod in UG's Official Gain Whores