Tundra Heatboulder
A loud thump resounds across the tundra followed soon after by a distant whistling. The noise rapidly grows louder and shriller until suddenly a superheated boulder appears in the sky, sent hurtling up by an immense blast of pressurized steam and now plummeting down to catastrophic effect!
Realize Danger. Any adventurer that makes a Nature or Survival check recognizes the unusual sound for what it is—their warning gives everyone advantage on ability checks, attack rolls , and saving throws against the tundra heatboulder
An Athletics check can be made to outrun the heatboulder’s impact and fallout, but anything moving with a speed of 35 feet or less has disadvantage. Although it requires excellent coordination and some luck in just a sliver of time (a single readied action), destroying the heatboulder (AC 18, 200 hit points) before it impacts the tundra results in a Critical Success.
Critical Failure: The party are right there at the impact site, taking 55 (10d10) thunder damage as a massive hole appears around them created by the heat of the boulder instantly melting the ice all around it. Each adventurer makes a Dexterity saving throw , falling into the pit on a failure and taking 21 (6d6) bludgeoning damage upon landing plus 35 (10d6) cold damage as the water refreezes. For every 10 points of damage taken, an adventurer loses 1 Supply .
Failure: The adventurers are near enough to the impact site to feel it, taking 35 (10d6) thunder damage and making a Dexterity saving throw , falling prone on a failure. On a failure by 5 or more the adventurer starts sliding down into the resulting pit at a rate of 20 feet each turn, unable to get up from being prone and making Acrobatics checks to crawl back up or falling down into the pit after 1d4 rounds of sliding and taking 21 (6d6) bludgeoning damage upon landing plus 35 (10d6) cold damage as the water refreezes. For every 20 points of damage taken, an adventurer loses 1 Supply .
Success: The adventurers manage to escape the impact of the tundra heatboulder and the worst fallout from its catastrophic landing.
Critical Success: The adventurers watch the tundra heatboulder land from afar, safe from harm.