Its eyes glowing like bluish-white flames amid the shadows of its kingly helm, this skeleton wields two fearsome scimitars.
Source: Mythic Adventures (Pathfinder RPG)
Everyone who has played any type of Dungeons & Dragons or Pathfinder should know what a skeleton is. Your animated bones of the dead. Walking mindless low level creatures created by foul magic. They have a tiny bit of cunning which allows them to use a weapon and wear armor. That is in a nutshell a Skeleton. They are your bread and butter low level foe.
A Mythic Skeleton is a rare version of your basic undead. It has powers your typical boneless wonder does not possess. Maybe they were created by ancient necromancers with a long lost rituals. They might be servant of a dark god. Ancient undead lost in time. There are a number ways you can make them special.
Combat: Mythic Skeletons use the Mythic Rules from Mythic Adventures. For the most part they are basic Pathfinder monster with maybe a new gimmick or two. The Mythic Skeleton is a Challenge Rating 1 monster with 1 mythic rank. Essentially a mythic rank allow them a pool of mythic power that can augment a roll or a special ability.
-Mythic Powers: 1/day. Once a day the Mythic Skeleton can augment a roll by 1d6. So if he attacks someone with 12 on a roll he can spend his mythic power to roll 1d6 and add that to his total. Possible hitting the target with that extra push.
-Defensive Abilities: Undead Traits, Channel Resistance +2, cold immunity, and damage resistance 5 against blunt weapons.
-Relentless: Any melee attack against the Mythic Skeleton provokes an attack of opportunity. A very cool ability that allows the skeleton multiple attacks. Each adventurer attacking him allows him to make an attack back.
-Superior Two-Weapon Fighting: A Mythic Skeleton fights usually with two weapons. They take no penalties for doing so.
For comparison your typical skeleton is Challange Rating of 1/3 and lacks Mythic Powers, Relentless, and Superior Two-Weapon Fighting.
I'm not a big fan adding more bloat on top of a complex rules system but I did find the monsters in Mythic Adventures enjoyable. The mechanics are fantastic and add another dynamic to the game. You can use Mythic opponents against non-mythic groups with no alterations. Just follow your challenge rating guidelines. They are a nice variation of your standard critters.