I got it to work, but since the the hanging and non-hanging giant spiders are different objects, the condition to drop a key on death wouldn't carry over after the spider drops from the ceiling. I applied it to a giant spider already on the ground, but prevented it from attacking until the player passes near a trigger sign. If there's a way to set the condition to spider once it drops from the ceiling, I haven't figured it out yet (create a condition based on a condition? I think it's possible..? EDIT: have the condition create a new oMsgSign containing the next condition - MAGICSIGNCEPTION).
spiderdropkey.lvl file (Editor Plus, playable):
http://www.mediafire.com/?lvkpy5322p5tl3zBreakdown/lesson:(assuming use of better sign editor by pressing M or middle-mouse on signs, + it allows you to copy/paste text)
Sign to create giant spider (add what's needed to your existing Spider Queen):
?oGiantSpider?hp=40?status=2?loot=""
Creates giant spider with 40 hp, in the "RECOVER" status that will prevent it from moving or responding to anything. Loot is emptied to prevent it from dropping paste.
Sign to make spider drop key on death (must be loaded after the sign above - place on right side or below previous sign):
%AoGiantSpider,Vhp,OA<%?oKey?x+=16?y+=24
The condition is between the two "%", the rest of the sign is what happens when the condition is met.
The nearest oGiantSpider is assigned to be the associated object for this condition. When its hp is less than 1 (default number for variable checking is 1, so we don't have to set it here), create a key. We've offset the x/y position so the key is created at the center of the spider's sprite - otherwise if there is a wall/ceiling to the left of the spider when it dies, the key could get stuck there.
Sign to 'wake' the spider when the player passes nearby:
%ToPlayer1,D32,O@%?!SET:oGiantSpider?status=1
When the target object (oPlayer1) comes within 32 pixels or less of the center (@) of this sign, put any giant spiders in the level into "BOUNCE" status, causing it to immediatly leap in the direction of the player, then carry on attacking as normal. This is placed at the entrance to the boss room. You'll want have the spider in a position where it's protected from any ranged weapons before this sign is triggered.