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Message: <blockquote data-quote="Greenfield" data-source="post: 5497422" data-attributes="member: 6669384">I questioned the skill check needed to create such a mirror, with a curvature so precise as to give it a focal point 231,000 miles away (presuming a lunar orbit).  We couldn't build that now, with the most precise machines we have.  Hell, we had to retro-fit the parabolic in the Hubble because of an optical flaw.  Dandu suggested a combination of skill, Aid Another and Moment of Prescience to give him a total bonus in the 60s.  I questioned "Aid Another" from an Unseen Servant, as well as using Aid Another to help a Fabricate, since they can't actually do anything to Aid.  We also determined that Moment of Prescience only applies to opposed skill checks, not just any skill check.  I also questioned whether a check in the 70s or 80s (adding in the presumed dice roll) would be anywhere close to doing the job in any case.In reality, making a mirror optically flat enough to just reflect accurately at that distance is just about as hard.  Let's pretend that a deity could and would give you that answer.  I'm sure there's a patron deity for hair brained schemes out there, after all.  We have gods of everything else.Now that you have it, how will you put it into use?  How will you make such a mirror, when the curvature would be imperceptible to the human eye, or any known instrument.  Seriously, there's such a thing as "margin of error", and in this case that margin is less than a micron.  There isn't a polishing compound fine enough to avoid leaving micro-scratches larger than the grinding tolerances would allow for. The minor changes in shape from movement stress and temperature variance will add more irregularities to the mirror(s).  Remember, a thousandth of a degree makes a huge difference over a course of over 200,000 miles.  Here's where we get back to the difference between game rules and the laws of physics.  The castle would be considered Colossal size, giving you a +8 to hit it.  The County or Barony it was in would be considered as Colossal size as well, as would the nation, the continent, and in fact the planet itself.  Colossal is as big as the scale gets in the game rules.  You could invent a term for something bigger, but at that point you're back to ignoring the actual rules.As for the precise focal length:  You're right, who cares if you're off by a few miles.  Less damage over more area, or more damage over less, it works out the same in the end.  The question is more a matter of whether you have any focal point at all.  Does your immense mirror (that can't actually be Fabricated at that size) actually bring all that light into focus on any point at all?    First, I never said aluminum would do the job.  Second, neither Adamantine nor Mithral are indestructible or unalterable in D&D.  Maybe you're thinking of Adamantium, from Marvel Comics?  And even there, there are powers that can break it.  In both universes, their "ultimate metal" can be bent, even if it does tend to spring back.  How you would Craft an indestructible, unalterable metal is, of course, another problem, but we'll ignore it for the moment.Would diamond work?  It's actually the preferred material for high precision reflectors in the real world, but even carbon crystal, the hardest substance known, expands and contracts with temperature changes.  Your huge reflector would still distort with heat, even if you had some way to grind it to that impossible precision.  (Which you still don't.)You can invent any spell you like.  You could even specify that that it will somehow stack with itself.  We're getting back to that "ignore the rules of the game" issue, of course, but we'll ignore that as well.You still can't hit your target at that range.  And you'll need to roll that attack roll 365(24(60(10*1D4+1))) times, taking a standard action per attack, while your target is shifting away at a thousand miles an hour (surface velocity of a rotating earth-sized planet with a 24 hour day).  By the time you've lined up your 5th reflector, the first one is off target.  You'll be spending weeks setting up the attack on a target that's gone from sight in 12 hours.  There are two ways to make it work.1) Use a cargo ship full of Wishes.2) Cheat.(Note, the two solutions aren't mutually exclusive.)Oh, there is anther way.  Create an Artifact, the Wrath of Pelor.  Its power is that it will send a beam of sunlight unerringly at any target in sight, doing damage based on the amount of sunlight striking it.  Now build your array of mirrors, all focused on a single point a few hundred yards away.  You can Take 20 on the aim, trying again and again as you fine-tune it until you get it just right.  Since these aren't actual attack rolls (there isn't one with this method), Take 20 is allowed.All that's left is building the orbital platform to mount it on, and we've already addressed that issue.  (Stone + Levitate + Greater Teleport + 12 Decanter's of Endless Water to use as maneuvering jets to build orbital velocity, add Wall of Stone again and again to create the platform itself.)Epic enough? <img src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f642.png" class="smilie smilie--emoji" loading="lazy" width="64" height="64" alt=":)" title="Smile    :)"  data-smilie="1"data-shortname=":)" /></blockquote>

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