Re: Halo 3 _will_ have online co-op (4 players!!)
Double post, but this is to keep my post from becoming cluttered. The skulls are on the left, their effect is on the right. The effects are based off the Halo 2 skulls of the same name, so it is possible they will havea different effect in Halo 3. The list of skulls comes from the official achievement list (9 skulls, one per level apparently, similar to Halo 2. Though it is entirely possible that there are skulls without achievements for them). Skulls in bold were not in Halo 2.
Iron- Reloads the last checkpoint when a player in co-op dies.
Black Eye- Shields do not recharge automatically, you must melee enemies to recharge them. Shields can be overcharged through this method.
Tough Luck- Unknown.
Catch- Enemies throw more grenades and all NPC's drop 2 grenades when killed.
Fog- Unknown. Some theories seem to think it will give active camo to the player (like the Envy skull in Halo 2) or permenantly cloak all enemies (like the Assassin skull in Halo 2), but those theories are based purely off speculation.
Famine- All weapons found have half ammo (only weapons with clips, not weapons with charges)
Thunderstorm- All enemies become the highest rank (all elites are gold, all jackals gold, etc)
Tilt- Unknown. The current theory is this skull will prohibit the use of weapons (like the TILT from pinball prohibits the use of the flippers)
Mythic- All enemies gain more health and shielding in relation to their rank (a blue elite gains less health and shielding than a gold, for example)
So Strubes, if the game was too easy, you could activate Iron, Mythic and Thunderstorm. You can't die, and the enemies will all be the highest rank with even more health and shielding then usual. In Halo 2, a Spec-Ops Elite's shield could take 2 charged plasma pistol shots before being drained. That would be very difficult on Legenadry even with 4 people. Turn on Famine and Black Eye, then you have much less ammo and are forced to enter melee range to regain shields.
So, in conclusion to this long post, Legendary with 4 people will likely not be that hard, but you can certainly make it much, much harder using the skulls.