Earliest Female Unit?

[Arilian]

. If you have Sprites, for example, you can bet that even in low-level Item Supression battles one of the towers will turn them into sheep...

It is true, also even true for boss fights, but time back is resurrect all units AND dispell the negative spell (often pygmy) AND you can use lvl 1 time back relatively early in the game.
Also you can dispell, and if the enemy control the lake faeries, the sprites can also dispell (this is not often needed but sometimes useful)

Is you have lvl 4-5 units probably it will cast lightning/armageddon killing some from each stack and you have a mutch harder task to resurrect everything.

[Zhuangzi]

You can definitely get around those guards at the gate to Demonis, BB. It is tough, and I remember once when I needed 10+ reloads to get it right. You've got to get through with enough room behind you so that you can get back into Underground Sea without the enemy stack being right next to you. It will stay exactly where it was when you went into Demonis.

It is worth it for Fire Rain though.

[BB Shockwave]

Thanks for the tip. I have not yet played the game through with a warrior and I plan to use an all-elven and later an all-demon army, so I'm gonna need the trick most likely.

In AP getting Demons is much easier, thankfully. You can get to Sheragga, the wandering Demon continent quite easily - the map to the continent is guarded by a quite strong troop just in front of the Necromancer castle in the Montero mines, but there is enough room to nab the scrool from behind them without fighting. There is a catch though - you cannot fly on Sheragga. But the enemies are easy to evade, and you can guaranteedly find all Demon units there (as well as some Lizardmen units), some even in "Horde" quantities. There also more items boosting demons then before. (Anga's Ruby no longer exists, but there is an armor-bearer and another item that increases female unit's attack and initiative).