Yes. He can bring in either Rebel or New Republic pieces and the Ossus Guardian has affinity for New Republic, so Garm can bring it in.

No, Ossus Guardians ARE NOT New Republic pieces. There's a difference here. Granted, I think it's going to require NickName to put it in the Mini-FAQ to be sure, but I'm about 98% positive that you will not be able to do this.

Garm is allowed to bring in pieces that are Rebel or New Republic. The Ossus Guardians are in the Vong faction. The fact that they have Affinity for New Republic does not change the fact that they start out as Vong faction. They do not become New Republic faction until they are already included in a NR squad. Very small distinction, but an important one, nonetheless.

No, once you join another faction because of Affinity, you are considered to be that new faction.

Take Princess Leia (A&E) and Han Scoundrel, for instance.

If you bring both of those into a New Republic squad via Jacen and Jaina Solo, Leia cannot use her CE on anybody, because her CE requires a Rebel follower. Han is now considered a New Republic unit because he was brought into the NR squad through Jaina's Affinity.

EDIT: Where the confusion comes in has to do with Reinforcements I believe. If you bring a Rebel piece into a NR squad using Garm's reinforcements, then those are still considered Rebel pieces. So you could bring Princess Leia into a NR squad because of Jacen's Affinity, and then bring in a non-Unique Rebel follower through Garm's Reinforcements, and THEN Leia could use her CE on that piece.

No, Reinforcements does not change a character's faction, only Affinity. Characters brought in via Garm's Reinforcements would retain their original faction.

Garm cannot bring YV into any team.

Yes, it's a timing difference. Garm's reinforcements happen 'during setup', which is after your squad has already been established. Factions only change because of Affinity during squad construction. You still have to be careful with things like Palpatine Sith Lord or Clone Commander Gree though, as they have Commander Effects that allow pieces to enter your squad, but those aren't the same as affinity, so they don't actually change the faction.

No for essentially the same reason. It is a Sith squad that can include Mandalorians, key phrase there is it is a SITH squad.

What if mandalore the Ultimate was in a squad with Ulic, what faction is it?

It was built as a Sith squad, even if everyone is a Mando.

In Mandalore the Ultimates case as entering a sith squad via Ulic, Ulic can bring Mandalorians on sith. Now when Mandalore Ultimate comes onto a sith squad he remains Mandalorian, & then he gets Mandalorian Conscription. So then ulic becomes mandalorian & also any fringe pieces or other sith you have in the squad. But technically bringing Mandalore the Ultimate on a sith squad as Ulic's CE states, he can only bring in mandalorians anyways.

Now if you do bring mandalore the ultimate on a sith squad via Ulic, a sith commander who effects specific "sith pieces". like if a piece has a CE that says sith followers with in 6 squares gain this ability, then there CE would not work in this case because Mandalorian Conscriptian specifically states that all figures become mandalorian for the rest of the skirmish.

So bringing a figure in via Affinity is just bringing that figure in. Its original faction stays & wouldnt be effected by CE's or SA's that effect other figures from the faction it just came on. The faction they have stays the same. Vong stays Vong, Rebel Stays Rebel. The only time a piece would be changed is in mandalore the ultimates case & only because he has a specific special ability that allows him to do it.

lol i hope im right in what i just wrote because i would look like a real duche if i wasnt lol..

well EmperorDragon thank you very much for pointing out im a duche lol nah j/k. i just noticed you clearified it up too. after the fact i wrote lol. But i was right on the rest?