I had a game at my house last night and we encountered a few questions...hopefully I can remember them all.
1. Is the Poison ability reduced by any of the damage reduction abilities like Toughness?
2. What does the symbol mean?
3. Could someone PLEASE explain how the Master Chief Arbiter figure works with the duo stuff?
4. What happens when a figure gets knocked back onto an allied figure? An opposing figure?

I think that is it for now...you guys feel free to tell me to #### off and go look it up but everyone here seems so knowledgeable and willing to help. I'm just slightly OCD and hate the fact that we may not be playing by the rules, exactly. Thanks in advance.

Sweeny.

1. yes, sure, toughness negates poison damage pretty much.

2. basically, willpower.

3. you attack with the MC/Arbiter without using any powers using the printed AV and damage (if no modifiers), roll dice, then do another attack with MC/A at -1 to damage, roll dice. that's all there is to duos.

4. you stop in the square in front of them, either friendly or opposing, you don't go past them. consider it your allies catching you, or you sprawling into your opponents.

So basically everything that the card says, and Willpower?

Yep. It's a good ability!

Question 1:
　
POISON At the beginning of your turn, give this character a free action and deal 1 damage to each adjacent opposing character.
　
TOUGHNESS Damage dealt to this character is reduced by 1.

Toughness reduces damage dealt by 1. Poison deals 1 damage to each adjacent figure. Since toughness reduces damage dealt and poison deals damage, it would reduce damage dealt by poison. Invulnerability and Impervious Reduce damage dealt also so they would reduce poison also. Good way to look at it is anything that reduces damage dealt, reduces damage dealt by poison

Question 2:

　
A character with the defense symbol possesses the Indomitable ability.

INDOMITABLE
This character can use Willpower.

The symble grants possession of the Indomitable ability. The Indomitable ability grants the use of willpower.

Question 3:

　
A character with the symbol possesses the Duo Attack ability.

DUO ATTACK
Give this character a power action to make a duo attack. This character possesses for this action. It makes a close or ranged combat attack as a free action. After the attack resolves, it may make an additional close or ranged combat attack as a free action with its damage value modified by -1 to a minimum of 1. If this character is defeated or loses Duo Attack as a result of the first attack, the second attack is not made.

Question 4:

KNOCK BACK DAMAGE
A character’s knock back path can’t continue beyond a square that blocks movement, elevated terrain of a higher elevation or the edge of the map. If it would do so, the character’s knock back path ends in the square before its path would cross into any of these areas, and the character is dealt 1 damage, as shown in Figure 10. This damage dealt is called knock back damage. It can be reduced as normal and is applied separately and after damage dealt by the attacker. Knock back into a terrain feature does not destroy it.
If the knock back path would cross a square occupied by another character, put the knocked back character in the last unoccupied square adjacent to the square occupied by the other character. Stopping in this way does not deal damage to either character.

I have also inncluded a link to the download section on the http://heroclix.com/downloads/heroclix-rules/ website.

Welcome to the game and enjoy!

I will not answer the question because it has been already. However I would like to point out the Heroclix Rules part of the forum where you can usually get a quicker and more accurate answer. Plus, the official rules deputies post there too.

Link to the rules part of the forum.
http://hcrealms.com/forum/forumdisplay.php?f=50