Dust Explosion - Grain, flour, wheat

[Varyon]

Originally Posted by Anaraxes

A half sphere of 50 m radius is 4 / 6 * pi * 50^3 = 261,000 m^3. At 750 g / m^3, that's nearly 200 tons of flour. Whatever the genie can do, 50 mages still need to carry 4 tons of flour each.

At the 2 ton total given previously, you can manage 2418.67 m^3. You'll only need a cylinder around 2 meters high (if that), you can manage a radius of 19.62 m, or around 21.5 yards. If 1 meter high is sufficient, you could manage around a 43 yard radius.

Let's say the djinn is able to take those 2 tons of flour and make a 15 yard radius of more-or-less optimally dispersed flour in a 2 yard cylinder. That's 1080.86 m^3, or 810.645 kg. That's the equivalent of a little over 7000 lb of TNT. Let's go instead with a suboptimal dispersion that only manages the equivalent of 2,500 lb of TNT (note this means only a little better than 15% of the flour properly detonated). That's 6dx100 damage at the epicenter, and (as a thermobaric explosion) you divide by distance in yards to determine damage elsewhere. Against most foes, 15d injury is pretty much guaranteed death, 10d is likely death, 5d is possible death, 3d is likely incapacitation, 2d is possible incapacitation, and 1d will cause lower-quality troops to feign death or flee. As this is an explosion, Large Area Damage Reduction (LADR) will typically be around 50% (for partially armored targets) and 75% (for fully armored targets) of Torso DR. See the following chart.

LADR	15d	10d	5d	3d	2d	1d
0	40	60	120	200	300	600
1	39	58	113	182	262	466
2	38	56	107	168	233	381
3	37	55	102	155	210	323
4	37	53	97	144	190	280
5	36	52	93	135	175	247
6	35	51	89	127	161	221
7	35	50	85	120	150	200
8	34	48	82	113	140	182
9	34	47	79	107	131	168
10	33	46	76	102	123	155
11	33	45	73	97	116	144
12	32	44	71	93	110	135
13	32	43	68	89	105	127
14	31	42	66	85	100	120
15	31	42	64	82	95	113

Even if the 1000-man enemy reserve has LADR 15, if it's arranged with 1 man every 2 yards in a roughly square formation (for roughly 60 yards by 60 yards), a dead-center "hit" will instantly kill (15d+ injury) roughly 80% of them, and the rest will be critically wounded (10d+ injury). If the epicenter of the blast is 30 yards from the center of the formation, you'll instantly kill (15d+ injury) roughly 40% of them, critically wound (10d+ injury) another 30%, and seriously wound (5d+ injury) the remaining 30%.

If the mage successfully pulls this off, expect him to invest in acquiring some large quantities of flammable dust (sawdust, flour, coal dust, etc) and making heavy use of it in future engagements. Unless the enemy figures out what he just did, however, and opts to dedicate a large deal of their magical oomph to countering it (which is still a strategic victory for the PC, as the enemy will be diverting a lot of resources).

EDIT: I should also note that using this may be extremely demoralizing to the enemy, at the very least requiring some penalized Fright Checks by the less-disciplined troops. If the enemy is likely to realize what you did, it may be worthwhile to load some ballistae with flour bags afterall. Not so you can repeat the action (I'm assuming the djinn is only going to be available for 1 summoning during the battle), but because the enemy doesn't know you can't repeat it - after seeing half a brigade vaporized after being showered with flour, getting hit with flour oneself will likely call for a Fright Check to avoid an unplanned retreat.