I found the wonderful obsidianmese tools mod by SaKeL that was originally on the (now taken down) SurvivalX server.
I have edited it so that it will fit well with other mods on sara's survival, and gives more flexibility with settings
Here it is:
I removed a few items that were originally in the mod because they did not fit, and tested the mod on my computer to see that it worked, and added settingtypes for more control over behavior of the mod
Here are the features:
obsidian mese sword: made with mese crystal and obsidian shards. A pretty good sword
obsidian mese sword engraved: uncraftable, intended to be dropped by mobs. On rightclick, it shoots an obsidian shard which can deal damage. It can also explode when it hits a node. Define this behavior in the settings.
obsidian mese pick: a pretty good pick
obsidian mese axe: removes all tree nodes above the one cut. Craftable with 1 block of mese + 2 mese crystals + 2 obsidian shards
obsidian mese shovel: a good shovel, compresses soil to make a path on rightclick
obsidian mese hoe: can hoe 4 blocks in a row at once
also adds: meseapple which restores full health when eaten, but is kindof expensive
the itemname of the engraved engraved sword is: "obsidianmese:sword_engraved"
It does not have a recipe, and is a powerful weapon, so it should be dropped by difficult mobs.
I would suggest that you make imps (in the nether, and fire imps) have a 10% chance of dropping one
I would also suggest that there is a chance that other hard mob drop some of these tools: they make a good reward.
the minetest forums page: https://forum.minetest.net/viewtopic.php?f=9&t=24353&p=368898#p368898