Other Devil variants?

[true pond]

We have dust devils and smoke devils which have names after the combo runes. So why not introduce mist, mud, steam and lava devils?

Mist, Mud and Steam could be a new mons release with Sailing as it would be in accordance with being on the water.
With this, it could be that they are apart of a boss instance when sailing and their island could be surrounded by elemental warriors:
Mist - air, water and maybe ice warrior’s
Mud - earth, water warriors
Steam - fire and earth warriors

This would be 6 new mons just from this spot, as well as give a new spot to kill earth warriors

Lava devils could be a new high level slayer monster added requiring maybe 96/97 slayer(since lava is a higher req than smoke and smoke is at 93)

[ember grove]

Lava devils sound like they would be really cool. It might fit well with Sailing, unlocking new areas where you could find each of these variants. How would slayer masters assign these? Would you need to find the islands first to be available to unlock them?

[weary marsh]

We could also call those places "Resource Islands"