Critters III! Now also in 5e!

[Metastachydium]

Drei

A DINOSAUR! (Kind of.) And a strong, tough, thoroughly crazy one at that. It truly is what a Chaotic beast touched by the Far Realm should look and work like.

Armor Class: 23 (-2 Size, +15 Profane), touch 23, flat-footed 23

Call me old-fashioned, but I think unusual bonuses to AC should appear noted somewhere among the SQs. Something amounting to the conversion of all natural armour bonuses into profane (which would seem to be something that happened to this dino at some point) could be interesting, for example. Also, I think something like deflection or luck would probably fit better than profane, given that Drei's CN.

Saves: Fort +15, Ref +5, Will +13

Will should be +11, I think.

Regeneration (Ex) The Regeneration ability of the Drei does not work against damage done by weapons/spells with the Lawful descriptor.

I think I'd rephrase this; weapons can do Lawful damage, but I don't think they come with a Lawful descriptor attached.

Pale Shark

How to make a shark amphibious? Kill it dead and put some legs on it!

Special Attacks: Toxic Bite, Wounding Bite

Wounding is a confusing name; it usually denotes stuff that bleeds profusely and has extra damage hence, mostly CON, I think? "Weakening" would mayhaps work better. (I'd also remove the reference to disease in the description of Toxic Bite, incidentally.)

Special Qualities: Darkvision 60', Undead Traits, Dark Vitality, DR 5/Slashing, Blood Healing 5, Sense Living 60', Blind, Blood Scent

(…)

Skills: Climb +11, Jump +12, Listen +6, Move Silently +6, Spot +6, Swim +12

So, um, this thing is Blind. And it has 2 ranks in Spot. Why's that?

Pale Horse

And behold a pale horse! That's actually a normal and decent person! Nice one again. (And the idea that Plants are, generally speaking, safer around them than the vast majority of non-mindless living creatures is just the lovely cherry on top.)

Aura of Death: Any creature must make a DC 17 Willpower Save if they are within 60 ft. of a Pale Horse (Save DC is Charisma based). If the opponent succeeds, he must still make another Save while he is within range of the Horses Aura, and the Save DC gets a +1 Bonus for each 10 ft. closer the opponent gets to it.

The text doesn't clarify the frequency of saves needed. I'd recommend a phrasing more like, say, this:

"Each round, any creature within 60 ft. of a Pale Horse must make a DC 17 Willpower Save (the save DC is Charisma-based). Even if the opponent succeeds, he must still make another Save every subsequent round while he is within range of the Horse's Aura, and the Save DC increases by 1 with each 10 ft. the opponent covers between himself and the Horse thereafter."