My game is an open-world co-op MMO with retro graphics, permadeath and no leveling system.
The problem I'm facing, is the fact that I don't know how to make some monsters appear harder than others. Since nothing has a level, and characters can only get stronger by acquiring better items, it's difficult for me to "warn" players that a monster is difficult for them.
Fortunately, the whole world is designed by hand and we know which areas should be more difficult than others. So this means, I as developer knows which monsters are stronger than others.
But new players won't! I don't want them to get frustrated by walking into the wrong monsters reserved for higher players.
So then, how can I make monsters appear more dangerous than others?
Some things I thought of:
increasing the size of the monsters: This could work but it's not a valid rule for everything. For instance, the end-boss has small minions which are also powerful.
use of particles: I remember from playing WoW some monsters who were stronger excessively used particles to make them appear more powerful:
dividing the world into danger levels: Here I would add a danger level or something to the HUD that displays whether the player is in a safe zone or somewhere dangerous. It would change and display a notice whenever the player moves to a different danger level. Do-able although I have no clue how to portray it on the HUD.