Thoughts about pincers… you know, the hand held set of tools called pincers can be used one handed (if you have big enough hands and a strong grip that is). However, when I try to picture “a large set of iron pincers,” I think of some pretty massive items that even someone as strong as a shimnus is likely to be needs to hands to wield it. Also, both weapons are identified as “magical weapons,” with the pincers given a +1 to hit, and the iron hammer a +2 with 1d8+2 damage.
Giant Form as written it is close, but not quite right. I take “once per day, the shimnus can enlarge itself to the size of a storm giant” to mean not so much that the shimnus looks any different, just bigger. I don’t think Giants even need to be mentioned in the writeup – this is just a size change, so it only needs to be said that she takes on Huge form. (hey, can we take some inspiration from either the ToH or WotC spriggan?)
Here is the spriggan’s size-changing ability from FF (maybe we can even do a secondary stat block like the spriggan got):
Size Change (Su): At will, spriggans can change their size in a fashion similar to the effect of an enlarge spell. The size change from Small to Large gains +8 Strength, -4 Dexterity, +6 Constitution and –2 to attack bonus and Armor class. A spriggan’s short sword has the same attributes as a Large short sword when enlarged. An enlarged spriggan is unable to make a sneak attack or use it spell-like abilities.
Let me give it a try here:
Size Change (Su): Once per day, a shimnus can change its size in a fashion similar to the effect of an enlarge person spell. The size change from Medium to Huge grants a +16 size bonus to Strength, a –4 size penalty to Dexterity (to a minimum of 1), and a –2 penalty on attack rolls and AC due to its increased size. Its natural reach increases to 15 feet.
(the second paragraph here might not even be necessary, as we can say that this ability is otherwise like the spell? Keep the 10 round maximum notation though.)
If insufficient room is available for the desired growth, the shimnus attains the maximum possible size and may make a Strength check (using its increased Strength) to burst any enclosures in the process. If it fails, it is constrained without harm by the materials enclosing it. The shimnus can remain in giant form for 10 rounds.
I’d prefer to spell these out:
Rock Throwing (Ex): While enlarged, a shimnus can hurl rocks weighing 60 to 80 pounds each (Medium objects) up to five range increments. The range increment is 140 feet for a shimnus’ thrown rocks.
Rock Catching (Ex): While enlarged, a shimnus can catch Small, Medium, or Large rocks (or projectiles of similar shape). Once per round, a shimnus that would normally be hit by a rock can make a Reflex save to catch it as a free action. The DC is 15 for a Small rock, 20 for a Medium one, and 25 for a Large one. (If the projectile provides a magical bonus on attack rolls, the DC increases by that amount.) The shimnus must be ready for and aware of the attack in order to make a rock catching attempt.
Since you had me looking at night hags anyway, I think I like their damage reduction 10/cold iron and magic.
