agree with the extra skills, and DEX to saves
Speaking of DEX, is Dexterity 15 like a regular Stone Giant enough?
A Lich has DEX 16 (+3), which is quite decent for a spellcaster, so I'd consider giving the Dodkong DEX 17 (+3) which'd also bump its AC up to 18.
add terran and undercommon (languages)
Makes sense.
The 5E Lich has five extra languages, but it also has a much higher INT than the Dodkong. Terran and Undercommon makes two languages, so its INT bonus matches the number of bonus languages like the Lich's five does.
You might have noticed I didn't mention the rough draft's
Saved by the Shadows in the above.
The descriptive text for that is identical to
Legendary Resistance so what's the point in renaming it? Just give it
Legendary Resistance (5/Day) instead.
Or alternatively, tweak the ability so the "Shadows" has some relevance.
Like, it doesn't work if the Dodkong is in sunlight, or it works like the
Sacrifice Minion idea I came up with for souped-up version of the Cleon Special Cairn Wraith.
Thus:
Saved by the Shadows (X/Day) A. If the dodkong fails a saving throw while in dim light or darkness, it can choose to succeed instead.
Saved by the Shadows (X/Day) B. If the dodkong is hit by an attack or fails a saving throw, it can choose to sacrifice a shadow under its control that is within [60 (or more?)] feet. The shadow is destroyed, but the attack misses the dodkong or its saving throw succeeds.
The latter would require the Dodkong have a retinue of shadows to burn up to make saving throws.
However, if it has the Cairn Wight version of
Death Grip it already creates shadow minions, plus it's easy enough to add some trait and/or ability so it usually has a retinue of shadows around it.
Or just give it standard
Legendary Resistance (X/Day).