How to safely drop victims into the Tayan’s mouth?

Roll them

The victim's hands and arms are tied to their sides and their legs are tied together at the ankles. Then the victims are rolled down a steep slope into the Tayan's mouth.

The ramp can be facing the Tayan at a 45 degree angle. The bound prisoners are placed at the top of the ramp and roll down like logs into the Tayan's mouth. Even if they do not roll all the way into the mouth, the Tayan can pull them in with its tentacles.

Sometimes, prisoners use Houdini magic to escape their bonds. Either they jump off the ramp and run away before the guards can stop them, or they break out of the rope as they roll down the ramp. They use their arms to stop their roll, and by staying at the edge of the Tayan's mouth, they ensure the guards do not come after them. No one has ever been able to do it, but if they can jump over the mouth of the Tayan or walk around its mouth, all while dodging crumbling sand and the Tayan's tentacles, they can escape to the other side. If they take too long, either the Tayan will pull them in or the guards will surround the prisoner and force them in. The reason the guards is that prisoners rarely escape their bonds, let alone get around the Tayan.

Assuming rope

You can just use a rope to pull the victim into the mouth. You can engineer it up or keep it simple, depending on your story needs. Ex. two parties pulling the victim between them in a V shape where the two edges go clear of the Tayan's mouth, but the middle doesn't.

Guards use long poles with a crescent-shaped tip to push victims into the Tayans mouth. The victims need only have their hands restrained, then they're helpless against the push of 2 or 3 guards equipped with these poles.

Unfortunately, some sneaky victims won't accept their fate without a fight and try to dodge below or jump over the poles. Most escape fights last no longer than a few seconds because the sands are too unstable to be an effective fighting ground, but some lucky individuals manage to confuse their guards with their dodges. Especially junior guards loose their orientation and step too close to the Tayans maw in their attempt to catch their victim.

The Dalians worked out how to safely feed the Tayan long ago. They use a berry from a nearby oasis, which (also genetically engineered long ago) acts as a powerful sedative. Juice from this berry is served to each victim on the night before their execution. Those who drink it, soon pass out and don't awaken until the agony of digestion begins.

The area surrounding the Tayan mouth is surrounded by solid posts which have carefully measured ropes tied to them. The Guardsmen, each tie themselves to those ropes, then carry the unconscious victims toward the Tayan. When they run out of rope, they are at the edge of the safe zone. After tossing the victims forward into the sand covered mouth, the guards then pull themselves back up to solid ground using the ropes. It is a time-honored and effective ritual which requires a minimum of manpower while providing complete safety to the guardsmen who perform it.

The subtle flaw which this ancient procedure hides, is that the sedative, being genetically engineered, is unnaturally safe. The consumer cannot overdose on it by taking too much. They just end up sleeping a little longer than they would have on a smaller dose. Your main characters, with total trust among themselves, can distract the guards while the lightest weight person among them drinks the doses meant for the team's best fighters. From there, everything is set up for the undrugged characters to surprise the guards, overpower them, escape, while carrying their sleeping companion out of harms way.