# Thin Ice (CR 1+)

A frozen lake or river can prove a serious danger if characters misjudge the thickness of the ice. With a successful DC 20 Survival check, a character can accurately gauge the amount of weight a given sheet of ice can support. Table 4–7: Thin Ice lists the maximum size creature or object that can be supported by ice. (A Fine creature or object can be supported by any thickness of ice.) When a creature steps onto ice that is one category thinner than what could normally support its weight, the ice begins to creak and crack ominously—a warning that a creature can notice with a successful DC 10 Perception check. At the end of a round, if an area of ice is unable to support its load, it gives way on a result of 10 or less on a d20 roll. This roll takes a cumulative –4 penalty for each size category by which the creature exceeds the maximum size the ice can support. A creature that is prone is treated as one size category smaller than its actual size for the purpose of determining whether the ice can support it. Ice within 5 feet of a fresh break is fragile, and it is treated as one category thinner for the purpose of determining the maximum size creature it can support.

Table 4–7: Thin Ice
Ice Thickness Maximum Size Break DC
Under 1 inch Diminutive 5
1–2 inches Tiny 15
2–4 inches Small 20
4–6 inches Medium 25
6–12 inches Large 30
1–2 feet Huge 35
2–4 feet Gargantuan 40
Over 4 feet Colossal 50

When ice gives way, a hole of a size equal to the creature’s space opens in the ice. A creature falling into the near-freezing water beneath the ice is treated as if it were in an area of extreme cold, and on the round it plunges into the water, it must also succeed at a DC 15 Swim check or be submerged beneath the water and trapped beneath the ice, unable to surface. A creature trapped beneath the ice can attempt to break through with a Strength check (the break DC depends on the ice’s thickness, as indicated on Table 4–7), or it can attempt to swim to an opening in the ice (although unless the creature is able to see in the darkness beneath the ice, it might have trouble finding its way to where an opening is). A submerged creature that is adjacent to the edge of the break in the ice can attempt a DC 20 Climb check to pull itself out, although keep in mind that ice adjacent to a break is fragile and could shatter in turn.