Creature: Swamp Creatures

So again, something a little bit different. This time, I'm doing a monster concept. The first thing you may notice is that I did not include any stats. That is because the intention is for this to be more of a template than anything else. The monster may be encountered at any time in a campaign, so the stats will vary wildly while the concept remains the same. I included a list of characteristics that would make finding relevant stats easier, since one would only have to follow those guidelines. 
Also something new here: I want to build upon one of the very first posts I did here on this blog. That would be the one and only Black Forest. I'm going to spend the next few days making encounters or NPCs that could be found in there. Credit for this image comes from Deviant Art user ~orochi-spawn...though I still got it from Reddit.
Edit 7/16: So I just realized that I forgot to put the picture in...


Name: Swamp creatures
Environment: Swamps, Dark forests
Type: Aberration

Description:
The creature is large and grotesque. It has slimy green scales, and massive claws. It stands crookedly bipedal, and lets loose a terrifying roar as it sees you. 

Characteristics:

• Low intelligence
• Melee
• Heavily armored
• Amphibious
• Resistance to poison
• Toxic bite

Tactics:

• Charge forward
• Fight to the death

Info:
The Swamp Creatures are very dim-witted but powerful foes. They are created by perverse magic that corrupts the natural order of things. They are considered aberrations, and are unnatural. They feed off of any living flesh, but are not strictly hunters. They will eat what they kill, but the swamp creatures are driven to kill anything they lay their eyes on. They do not use any special tactics beyond hiding in pools of water until they see something to attack.
In combat, the swamp creatures are very predictable. They charge towards the nearest enemy and attack until it dies. Then they move on to the next enemy. This continues until there is either nothing left to kill, or the swamp creature itself is dead. The creatures are strong physically, and are heavily armored, with a resistance to poison. They have no special powers or magical abilities beyond a poisonous bite. 
In terms of roleplaying, the swamp creatures are created mostly by accident. They are products of corrupted nature, and are driven insane. They used to be other creatures, but have been so greatly altered by magic that they are unrecognizable. They sometimes may hunt in packs, but it almost always ends in them tearing each other to pieces until only one remains. Even that one will probably be so heavily injured that it dies shortly thereafter. They may be used by the antagonist as low-level flunkies, as they are very easy to manipulate into serving simple tasks. Mostly just to guard a particular area. They are not very good trackers nor watches, and they can be simple to sneak by unnoticed.