Molten metal? Oil? Who knows...
Anyways, idea: a Mega Man series romhack where you play as a samurai and gains special techniques by defeating ancient demons. The techniques would use an "Ougi" gauge shared among them all (similar to Mega Man Xtreme 2's Zero), but can be recovered by finding cups or bottles of Holy Saké, killing enemies or getting hit (though the gain from killing enemies would be minimal, cups or bottles would restore 1/8 to 1/4 of Ougi, taking damage would restore based on damage taken). By default, your main weapon is... Your sword, a short-ranged attack. In 5 however you could get a Mystical Bow, which has infinite arrows but does mediocre damage, thankfully the arrows are strong enough to hold your weight. And... Well, different powerups, different replacements.