DnD Sex Edition

The aboleth are amphibious sea creatures that are all hermaphroditic and lay eggs (source).

Due to their deep sea living and elongated facial protuberances, their mating is based on the tripod spiderfish.

The aboleth is surprisingly easy to seduce. They commonly reproduce by self-fertilization but will mate with any other aboleth they encounter. If a PC cast an illusion of an aboleth, for example, the initial seduction DC could be as low as 5. Mating happens only underwater and drowning rules will be in effect throughout this scenario.

If the PC makes a seduction attempt while on land: A large tentacle extends out of the water and wraps around you, pulling you abruptly into the water. 

Make a DC 14 Con save to determine if they are poisoned. On a failed save, the PC can breathe underwater but cannot exit the water without penalty as outlined in the aboleth stat block. On a success, the PC is responsible for breathing underwater.

The large sea-green fish creature pulls you deeper and deeper. As the surface light fades away and the pressure of the water begins to mount, you’re released and float just above the rocky underwater terrain. They swim around you with interest, flashing an orange-pink belly. Deep in your mind, you hear an echo: “Let’s see if you’ll be a worthy mate or if I’ll have to do it myself.” Moments later, the water is flooded with a cloud of stringy mucus. You realize that you’re swimming in a pool of the aboleth’s sperm. Nearby, a larger orb floats in the pool: the aboleth’s egg. The sticky warmth is somehow appealing to you and you reach down to remove your clothes to begin working yourself towards your own orgasm.

Make a DC 15 Performance Check. Advantage or +1d4 bonus to the roll if PC is enlarged to at least large size.

On a success: The orgasmic cloud you release into the water is smaller than that of the aboleth’s but they seem pleased nonetheless that you’ve made an effort. The creature gently follows its sinking egg down into what you now realize is a rocky nest they must have built. “Your presence is no longer needed” echoes the alien voice through your head.  The PC and their allies are able to ignore all lair effects of the aboleth for 1d4 days..

On a fail: the aboleth attacks with a tentacle attack in a surprise round.