Base Metals has several metal-specific abilities -- extra power against undead, slow auto-repair, etc. -- that spices things up. Why not add the same to Modern Metals, but with modern-style effects:
- Items made of magnesium can light fires, just like flint-and-steel. Magnesium boots may light fires randomly.
- Items made of plutonium can give poison effect every X ticks. Plutonium block can do so at a distance or on collision.
- Items made of uranium can do the same as plutonium items, but less often.
Base Metals has several metal-specific abilities -- extra power against undead, slow auto-repair, etc. -- that spices things up. Why not add the same to Modern Metals, but with modern-style effects: