Monster Proficiencies

In 5e, the vast majority of monsters do not get a Proficiency Bonus to either skills or Saving Throws. This is bad:

• Strong or quick monsters cannot pass Athletics or Acrobatics checks as would be expected
• Creatures that should have good Saving Throws (an ogre subjected to a CON save) has a much higher chance of failing, which doesn't model the monster well
• Monsters with a lot of mass (size Large or larger) or smaller mass (size Small or smaller) should have modifiers that reflect their innate nature. The same goes for creatures with a lot of legs (or no legs at all!)

To address this issue:

• All monsters will receive a Proficiency Bonus for skills and saves they should be 'good' at
• This bonus will be based on the monster HD as if it were character level
• A creature known for a particular ability (e.g. octopus or constrictor snake using Athletics to grapple) will get a double proficiency bonus in the relevant skill if it does not already have a suitable bonus to its signature ability
• Creature size and number of legs will matter: grappling or knocking down a strong, large creature (like an ogre or a horse) should be a lot harder than knocking down a human with the same strength stat. The same goes for small creatures; they should be easier to take down.