The Pool of the Dejected Rusalki

The Hill Cantons blog has organised a small 'competition'. Each contestant had to write a short Eastern European-flavoured encounter. The winning entries would be included in Hill Cantons' upcoming sandbox supplement.

Well, apparently many contestants beat me, so I am publishing my entry on my blog.

John William Waterhouse - Hylas and the Nymphs

The Pool of the Dejected Rusalki

A dense wood of birch trees conceals this shallow pool. The pool itself is surrounded by immense weeping willows, which look like brooding green giants or trolls from a distance. The water is very still and greenish. All berry bushes in the area grow incredibly bountiful.

A long time ago, a wandering knyaz (knight) stopped here on one of his errands. The knight was insanely handsome, but somewhat of a womaniser, so he made up a tale of him knowing some magician who could transform the rusalki into normal women to take advantage of them and bed the rusalki — yes, all 12 of them. The pool is currently inhabited by the offspring of the knight and the original rusalki, who are much more humanlike than your average rusalka (-2 to any spell that detects or affects glamorous/fey creatures, etc.)
The rusalki are still waiting for their father to return, break their bond to the pool, and transform them into human females.

If a party approaches the pool, 2D4 rusalki will exit the water and start walking, all beguiling smiles, towards the most 'knightly'-looking character, e.g., one wearing full plate armour or, if no PCs wear plate armour, one who looks or acts aristocratic.

Now two things may happen:

(1)- The party doesn't take any offensive action.
The rusalki will ask the "knight" to enter the pool with them. If he resists, they will try and drag him into the pool. If the party becomes aggressive see (2) below; if not, the "knight" is carried into the pool where the remaining rusalki assemble and ask him to vow to return with the magician. If the "knight" agrees, the party will be left alone, and even provided food, water, and more. If the "knight" refuses, the rusalki disappear under water never to be seen again. In the following 1D6 days, any woodland creature encountered by the party will be extremely aggressive towards them. Double the occurrence of any woodland wandering monster roll.

(2)- The party becomes offensive.
Whilst the initial rusalki surround the "knight", 3D4 more rusalki appear from the pool (just their head and shoulders) and start gazing at the other characters. A PC must successfully save vs magic or under his wisdom [depending on your favourite rules] or become entranced by the sight of the fabulously beautiful rusalki. An entranced PC will just stand idly and do nothing.
The rusalki around the "knight" will try and grab him to bring him into the pool.
(2a)- If the "knight" resists or tries to harm them, the rusalki will animate the branches of the weeping willows. Each rusalka may animate 2 branches. The two branches attack in co-operation: whenever one of the branches has successfully hit (it attacks as a 4 HD monster), it entangles its victim, which cannot move or fight any longer. The other branch then tries to strangle the immobile victim (it needs a hit); from the next round on, it will start suffocating it (1D6 automatic dmg per round).
(2b)- If the "knight" does not resist, he will be carried into the pool where the remaining rusalki assemble and ask him to vow to return with the magician. If the "knight" agrees, the party will be left alone, and even provided food, water, and more. If the "knight" refuses, the rusalki disappear under water never to be seen again. In the following 1D6 days, any woodland creature encountered by the party will be extremely aggressive towards them. Double the occurrence of any woodland wandering monster roll.

The encounter does not end here, though. If the "knight" has vowed to return with the magician, he has put himself under a strong geas, per the classic fantasy 'geas' spell, to find a magician who can transform the dejected rusalki into human females.