This is what happens when you combine Quake level design and movement with Serious Sam enemy density. Quake is all about economical and precise enemy placement coupled with tight and narrow level design to get the player into as many interesting situations as it can by shuffling the level layouts, enemies and resources around while keeping the action going and flowing. Herald of Havoc is only concerned with throwing countless enemies at the player with some of them having chaotic danmaku-like patterns.
The action in Quake pulses with rhythmic qualities, in Herald of Havoc it's just unintelligible noise.

Genuinely might be my favorite modern boomer shooter. Everything in the game is there in service of making the core verb - SHOOT - feel as good as possible. I think Herald of Havoc understands catharsis in a way that few shooters - and even fewer games in general - understand. So often you're presented with a new powerhouse mack-daddy of a gun, and the very next room you enter is brimming with squishy grunts supplicating themselves to the gib throne.

Level design is top-tier throughout, the enemies are varied but each serve a distinct purpose, and your arsenal is genuinely one of the best-feeling of any other FPS I’ve played.