AD&D Monster Manual part 57

UMBER HULK: Umber Hulks debuted in Supplement I: Greyhawk, and I would like to take this opportunity to curse their very existence.  I've been playing a lot of Rogue on my phone lately, and the bloody Umber Hulks are doing my head in.  Whenever I'm having a good run, and hitting the lower levels with a decent character one of these bastards pops up, confuses me, and bludgeons me to death.  Bloody Umber Hulks.  I hate 'em.

Anyway. 

Umber Hulks remain mostly the same as they were in OD&D.  They still have a gaze that causes confusion on a failed saving throw, and they still burrow through stone at a rate of 1" per turn.  Both of these abilities receive minor tweaks in the Monster Manual: the confusion ability is given a duration of 3-12 rounds, and the burrowing is now at 6" per turn in loam.  Probably the biggest change that the Umber Hulk gets here is an alignment switch from Neutral to Chaotic Evil.  It seems to me as though they've been reinterpreted from beasts to intelligent creatures, and the addition of their own language bears this out.

There are some other fun additions.  We already knew that Umber Hulks love human flesh, but here it is said that they prey on anhkheg and young purple worms.  The physical description of the creature is outlined in greater detail, and thankfully it is no longer described as having a head resembling a "bushel basket". 

Stat Changes:
Hit Dice: Old - 8, New - 8+8; Damage: Old - 2 claws 2-12 and bite 2-8, New - 2 claws 3-12 and bite 2-10

UNICORN: Unicorns first appeared in D&D Vol. 2: Monsters & Treasure, and they've been given a lot of extra detail here.  The main details are retained: that they may be approached and tamed by a "pure and noble maiden"; their great magic resistance, as they make saves as an 11th-level magic-user; their ability to sense the approach of all enemies at 24"; and their ability to flee using dimension door, taking their rider with them.  The taming of unicorns by maidens has been clarified: any maiden must be elven or human and good-aligned to tame a unicorn; even then they have but a 25% chance.

A lot of new abilities and immunities have been added.  A charging unicorn now does double damage with its horn.  In OD&D, this was described as "fighting like a lance"; this may very well have been functionally the same ability, but the obfuscatory nature of the OD&D rules makes it ambiguous.  The horn is now considered a magical weapon (for the unicorn, not the PCs), and strikes at +2 to hit. The unicorn is said to be immune to all poisons, and the possession of a unicorn's horn is a "sovereign remedy against all forms of poison, gas included".  They surprise on a roll of 1-5, due to silent movement.  They're also immune to charms, holds and death magic.  All-in-all, it's a bunch of upgrades designed to make them harder to kill or capture.

Stat Changes:
Number Appearing: Old - 1-4, New - 2-5; Hit Dice: Old - 4, New 4+4; Damage: Old - 2 hooves 1-8 and 1 horn 1-16, New - 2 hooves 1-6 and 1 horn 1-12