The Spider-Oasi

The party approached the oasis, its fresh water sniffed out miles away by Trixie, Drom the desert rider's camel.

Fronds of a pair of massive palm trees were glimpsed over the sand as they neared the water, standing out over the normal stunted growth of the Cold Desert. The party found this odd, but approached cautiously, as their waterskins were empty. 

Drom scouted ahead. He spotted a few corpses. Humanoid, animal. Not unusual for a remote oasis to be bait for ambush predators. As he neared, he saw that the bodies were shriveled and desiccated, almost as if they have been sucked dry. He reined in Trixie.

As he pondered, the "palm trees" shuddered and arose, walking on knobby, twisted legs, predator heads with sucking mouth parts swinging to target the new intruders...

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The Spider-Oasi ("Walking Palm")

Not-quite-right massive “palm trees” at oases, appearing to have thick trunks and spreading, twisted roots. Ambush predators that arise from the sand to reveal spider-like bodies, grasping limbs, and sucking mouth-parts. Telegraph by husk-corpses.

AC 14, HP30, ATK 2 claw/stomp +5 (1d10), MV Close, S+4, D+1, C+3, I-1, W+2, Ch+1, AL N, LV6; Grab: If two successful hits, target is held. DC15 STR to escape. Ongoing 1d6 dmg/round as it feeds, sucking the victim dry. May continue to attack while feeding.

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The party was able to best the pair that they encountered. Drom lured one away (although not without damage to himself and Zanegar), and the second was felled by a fortunate web spell and fire. Need to have more at the next oasis....