One of the pairs of scimitars hung in the audience chamber are magic weapons. These are each possessed by a demonic spirit which can animate them, and they are bound to defend the Demon-Queen. When released and verbally ordered against a target (one of the scimitars can activated in this way in place of either movement or attacking for the round, or both can be set in motion by spending the whole round doing so) they will fly to the attack. Once engaged they will do their best to slay first the chosen target(s), then any obvious allies of those targets, and finally any living creature present other than the Demon-Queen. They cannot directly act against the Demon-Queen, and she can render them inert for the rest of the day with a word, but otherwise they are motivated to ensure their own defeat (thus sending the bound demons back to the abyss) although they are still bound by the restrictions above.
Being animated objects they are immune or resistant to many spells (charm and such in particular, as well as taking half damage from most elemental attacks unless of such power that they could melt / break tempered steel), although some spells may affect the spirits animating them that would not have any impact on mere magic weapons (protection from evil, dispel evil, etc.). However it will not be immediately obvious that they are possessed, and players are likely to think them simply dancing weapons. They are effectively immune to normal missiles (being too hard to hit squarely), but attacks with melee weapons may be effective if enough force can be put behind them (assume this requires a 16 or higher strength, but clever players may find ways around this restriction). Note that being magic weapons any mundane arms that are turned against them are liable to come off worse in the exchange. They count as having a base armor class of 3, although this is worsened to 6 when they are between an attacker and the Demon-Queen (as blocking incoming attacks counts as defending her by the letter of the spells binding them). Once enough damage has been done to the weapons they will be damaged enough that the demons are released from service, but in this case they will also not be in serviceable condition to be wielded by the PCs without extensive repairs.
The first of the two (which fights as a 6th level fighter with 38 hit points) has a +2 bonus and while animated it additionally fights as though wielded with a 16 strength (for a total of +4 to-hit and 1d8+4 damage). It moves at 30′ per round, but must remain within five feet of the ground and is not clever or agile enough to easily get around characters. If recovered as treasure it additionally has the ability to roll twice for damage and take the higher roll when attacking larger than man-sized creatures (but is obviously no longer animated).
The second (fights as a 7th level thief with 21 hit points) has a +1 bonus and counts as having an 18 dexterity (+2 to initiative rolls and a modified armor class of 0 when not blocking attacks). It moves up to 60′ per round, but can fly about at will and can trade flat-out speed for maneuverability, covering only 30′ but darting about like a hummingbird. In this second mode it can easily bypass enemies to reach characters in the rear lines, etc. If recovered as treasure it has the additional ability to once per day allow the wielder to make one additional attack at any time against any foe in reach, ignoring normal initiative (but provided that the wielder is actually capable of attacking the target).