OK. Thanks!
Moving along, here's my beefed up Icingdeath skeleton:
Gargantuan skeleton
AC 17 (natural armor)
HP 170 (11d20 + 55)
STR 24 DEX 10 CON 20 INT 6 WIS 8 CHA 5
Dmg Vulnerabilites bludgeoning
Dmg Immunities cold, poison
Condition Immunities exhaustion, poisoned
Ice Walk
Multiattack - Frightful Presence plus 1 bite and 1 claw attack.
Bite +10, 18 (2d10 + 7) piercing
Claw +10, 14 (2d6 + 7) slashing
Tail +10, 16 (2d8 + 7) bludgeoning
Frightful Presence multiplies its HP by 25%. I don't think I am supposed to multiply its hit points for its two damage immunities (cold and poison), though, because Step 9 talks about a creature having three or more resistances/immunities. 120 x 1.25 = 213. That's a DCR of 10. Its damage output, meanwhile, is only 32 per round, but it has a high attack bonus, so its OCR is 6. That gives it a final CR of 8! Not too bad. Still, I suppose it was a good thing that laughter proved to be its biggest weakness!
[FYI: I wanted to keep the Frightful Presence because, even though it's just a skeleton, it's a freakin' big one ... plus its crappy Wis means that the DC is only 10. It only got one PC with it during the battle.][/sblock]
For Hedrun, I've removed the damaging part of her freezing aura, removed her fire resistance, and downgraded her Freezing Burst legendary action so it only has a 5-foot radius and only deals 5 (1d10) cold dmg and 5 (1d10) radiant dmg on a failed save.
So her DCR should be 4 (73 hp + 40 effective hp for her two uses of Legendary Resistance). As for her OCR, that's now 10 (108 for one cone of cold plus 68 for two rounds of [x] divided by three plus 10 for Freezing Burst and 5 for the spike growth lair effect = 74, which is CR 11 minus one for a DC of 14).
That makes for a final CR of 7. Did I miss anything?