EDIT: Doing more thinking, I'm actually going for a near-human race after all, apologies. I'll get a list of 'differences' between them and humans shortly, after brainstorming.

Right, preliminary list of differences, as worked with Shienvien and a couple others:

- Eireannach have a lifespan of 320-ish. (As worked out by a simply 4d100 roll, suggested by one Alfhedil)

- There are two 'ethnicities' of Eireannach, the Forestfolk and the Highlanders.

- Forestfolk are smaller and leaner than Highlanders, and usually possess mottled-colour skin to blend in with the foliage and undergrowth. Forestfolk are possessive of superior agility and upper body strength to climb trees, hunt in the forests and scale obstacles - for example, a cliff face. Forestfolk are naturally gifted for reconnaissance or archery work, as their agility and upper body strength aids them in avoiding detection and shooting bows.

- Highlanders are stockier, thicker-set and broader, with less agility and more raw muscle power. They have tanned skin to cope with the harsh sun of the mountainous regions of the Contaetha.

That's as much as I've got so far, but I'm still brainstorming.