Try to guess by comparing the phalluses to faces.

The most noticeable difference between the statues is the look on their face, so you decide that the correct "key" for each hole should be chosen based on that. To get started, you pull on the phallus already inserted into the left statue. You breathe nervously as it seems to refuse to come out. Steeling your resolve you take a sharp tug, stumbling back a little when it finally comes out. Inspecting the piece you notice why it was so hard to remove; The base has a swollen knot that seems like it would just barely fit. The shaft is circled with ridges and the head is a slightly rounded cone with little barbs pointing back towards the base.

Evidently you don't want to put this one back where you got it from. You take a look at the other options. Either the one at the height of pleasure or the one that seems to be enjoying less intensely. For now you set it between their feet and consider the other two. Considering the most normal-looking phallus, you feel pretty sure it belongs to the statue with the reserved expression. Assuming your guess about the last one is right, the remaining piece belongs to the left.

Hesitating, you place them back on the slots in the order you've somewhat settled on. Taking another look, you rethink the order. The big one with the bumps probably belongs to the center statue. And considering the barbs, perhaps the less passionate statue should have the fierce looking one you removed from the left.

You rearrange the "keys" and review your choices. The lustful left stature gets the normal-looking phallus, the overwhelmed center gets the large studded piece, and the knotted member goes to the more restrained statue. You feel as sure as you could possibly be at this point. Steeling your resolve you set to put them in place.

You insert the phallus into the left statue first, gently and timidly pushing it in until it stops. Nothing happens. You push the next phallus into the center statue, feeling a little more confident. The room remains quiet as you reach for the last piece. You shove it gently into the last statue.

A grinding sound starts to echo below you. The floor below you starts to fall and form a set of stairs which you start to slip down a little. As you get your footing you walk the rest of he way down the staircase, eventually finding yourself entering what looks like a shrine. At the other side of the room you see large statue of a nude woman crouching down to extend an open hand. From here it seems like there's some sort of light inside the palm.

Walking forward you also see doorways to the left and right, making it seem there's a whole temple down here.