DARK SOULS: REMASTERED

This achievement requires upgrading a standard weapon to Fire +10. Vamos in the Catacombs can upgrade a standard weapon to +5, then to Fire +5, then to Fire +10. This requires the Large Flame Ember from the Demon Ruins and a total of 9 Titanite Shards, 10 Green Titanite Shards, 8 Red Titanite Chunks, and 1 Red Titanite Slab.

Unlike the Lightning, Crystal, Occult, and Enchanted weapon upgrades, there is no Fire or Chaos weapon to be found, so you will have to make one from scratch.

Titanite Shards and Green Titanite Shards are found in limited numbers as you progress and can be bought from some NPCs. Red Titanite Chunks can be found in somewhat limited static locations throughout the mid-to-late stages of the game (as guaranteed enemy drops or on corpses). The second Black Knight in the Kiln of the First Flame (the final area of the game) respawns and always drop a Red Titanite Chunk. You can find a Red Titanite Slab in a chest Lost Izalith.

Fire and Chaos reinforcements use the same upgrade materials. The game only saves when you back out of an upgrade menu, so you can get these two weapon upgrade achievements with a single Red Titanite Slab and 9 (possibly 8, but I believe 9) Red Titanite Chunks if you'd prefer to not have to gather 2 Slabs and 18 Chunks. You'll end up losing the resulting fully upgraded weapon by dashboarding right after the achievement pops (before backing out of the upgrade menu) but you will get your upgrade materials back.

For these two achievements, you'll have to have the Large Fire Ember and Chaos Ember from the Demon Ruins. Head to Vamos, give him both Embers, and have him upgrade a standard weapon to +5, then use the "Modify Equipment" option to ascend this +5 weapon to Fire +1. Back up and choose "Reinforce Weapon" to upgrade the Fire +1 weapon to Fire +5, which will require a total of 10 Green Titanite Shards.

Now have Vamos "Modify Equipment" and ascend the Fire +5 weapon to Chaos +1. Back up and choose "Reinforce Weapon" to upgrade the Chaos +1 weapon to Chaos +5. Wait a few seconds after applying the final upgrade (which requires 1 Red Titanite Slab) and the Chaos Weapon achievement will pop. Again, do not back out of this menu screen confirming that the weapon was upgraded to +5, but instead go to the dashboard and force quit the game, then restart the game and continue. You'll be back at Vamos as if you had never done the Chaos upgrades.

Now have Vamos "Modify Equipment." The far right option should allow you to revert the Chaos weapon to a +5 Fire weapon. Then choose the option to upgrade ("ascend") the +5 Fire weapon to +6, which requires the Large Fire Ember. Back up to Vamos' main menu and choose "Reinforce Weapon," then upgrade the +6 Fire weapon up to +10, at which point this achievement will pop. You can dashboard here if you'd prefer to save your Chunks and Slab for something else.

As always, refer to http://darksouls.wikidot.com for specific information relating to items or locations.