Three questions.

1. When I use Darkseids Boom Tube Invasion am I only allowed to put a max of 8 Parademons down since that's the most he can put down adjacent, even if the total build total is say 1000 points?

BOOM TUBE INVASION: Give Darkseid a double power action when there are no other friendly characters named Parademon on the map. For every 100 points of the game's build total, place a JLSG #B001 Parademon bystander in an adjacent square.

2. When I use superman Big blue boy scout ability, does the attacking character keep the attack roll they made against the other figure and then compare it to superman's defense, or do they make another attack roll?

BIG BLUE BOY SCOUT: Superman can use Invincible. Once per attack, when a friendly character within 6 squares and line of fire would be hit by a ranged combat attack, you may place Superman adjacent to that character so that he blocks the line of fire from the attacker. If you do, modify Superman's defense value by +2 for this attack, and the attack targets him, instead, even if it would be illegal.

3. If I am possessing a figure with say, ophidian, can I welcome him to the legion since he costs less than 50 points? if so can i give him an ATA such as lost legion? Will the possessed figure then have the legion of super hero keyword as well and pick up the ATA?

WELCOME TO THE LEGION: When you build your force, choose one character of 50 points or less. That character gains the Legion of Super Heroes keyword and "wing symbol" this game. If your force includes other characters with this trait, you may increase the point value of your chosen character by 50 points if this character doesn't use this trait.

1. No clear answer exists.

2. I don't think you roll the attack again.

3. Yes, Ophidian can be welcomed. Yes, Ophidian can get the ATA. Yes, the guy Ophidian possesses will be legion too. Yes, the guy possessed needs to pay for the ATA too.

so he becomes a member of the legion thanks to ophidian being welcomed, then can be payed for the ATA, im assuming there is no reason to actually give the entity the ATA.

For Darkseid there is a clear answer. If you can't legally place the Parademon, you can't place the parademon. There are only 8 squares adjacent to Darkseid. Therefore, only 8 legal squares to place Parademons.

If you want to use an ATA you need to pay for everyone with the required keyword. So you will need to pay 4pts to give Ophidian the Legion Lost ATA even though he won't benefit from any of the DC team abilities you can choose as he is off the map.

Just looked up ATA's int he rulebooks, and you are correct, all characters that fit the prereq have to have it ^-^

1) Agreed. It's always been ruled that when something says "adjacent" that it must be adjacent... if something can't be placed adjacent, then it can't be placed (unless there's a caveat to the power/ability, but this one doesn't offer such a caveat).

2) A_B thinks right... nothing in the power says it's rerolled, just that it hits Supes instead.

3) The others are also correct... and this was a trick used by multiple players in the top 16 at the last ROC event. Great idea that I never would have thought of, but it works!

3) THE RULE OF OCCUPANCY
Any game effect resulting in two or more characters occupying the same square, or characters, terrain markers, or objects occupying a square of blocking terrain, is prohibited (except for Debris markers, see Terrain, p. 12). If part of a game effect would cause this to happen, that part of the game effect is ignored. If moving or placing a character, terrain marker, or object would cause this, then the character, terrain markers, or object must instead move to or be placed in a different square. Characters using certain powers and abilities may freely travel through other characters and/
or blocking terrain, but if it will end its movement in the same square as another character or blocking terrain, the moving character must end its movement before entering the occupied square.

Well, no. Chasenos originally didn't actually require things to be placed adjacent to him because of the golden rule of occupancy. He required clarification to change that. Sometimes "adjacent" just means "adjacent or as close as legally possible".