Originally posted by SilverSpeedy:

Here is the seed currently playing (second seed): VSNKLzn9gX
1 stars mobs so far deer, boars, druagr, skeletons, grey dwarves (brutes, shamans, normal)
2 stars so far grey dwarves
only boss killed deer boss.

Starred mobs just become more common the further you venture away from center(spawn) and that is still rng that gets factored when mobs spawn.

Like others have said, there isn't any seed difficulty native to the game. Seeds will have nothing to do with monster density or strength unless you mod for it.

The closest thing to difficulty is how large the nearby biomes and which they are and how far away your bosses are.