Added to
Homebrews with those scores.
I went with 10 HD since a swarm of fine creatures contains more than 100 individuals, and 100 was the max listed in the original writeup.
Here are the crimson death's abilities that we may wish to port over:
Blood Drain (Ex): A crimson death drains blood, dealing 1d4 points of Constitution damage immediately upon seizing an opponent with a tendril. Each round thereafter that the opponent remains seized, the creature automatically deals an additional 1d4 points of Constitution damage. The crimson death craves blood, so it usually presses its attack until it can deal at least 12 points of Constitution damage.
Seize (Ex): When a crimson death makes a successful incorporeal touch attack, one of its tendrils wraps around the opponent. The two creatures are not considered grappled, but the opponent can break free with a successful Escape Artist or grapple check (grapple bonus +11). Upon seizing an opponent, the crimson death begins draining blood.
Lift (Sp): As a free action, a crimson death can telekinetically lift another creature or an object weighing up to 300 pounds. This ability works like the telekinesis spell (sustained force version, caster level 12th), except that it works only on an opponent already seized by a tendril of the crimson death. Against a struggling opponent, use of this ability requires a successful grapple check (grapple bonus +11).
Skills: *A crimson death's misty form makes it difficult to spot in fog. Before feeding, the creature receives a +8 bonus on Hide checks in smoky or foggy areas. After it has fed, the bonus drops to +4 because of its red coloration.