No, nightmares do not get pack bonus. Yes, you can use skill animal lore on any animal and the last page (page 3 of 3) tells you pack instincts yes or no. Pack instincts yes means +25% damage in pack (I think, not 100% sure on the +25% and what that adds to - mele, magic, skills, etc? - some clarity would be appreciated)
http://www.uoguide.com/Pack_Instinct Pack Instinct, introduced by Publish 16 in mid-July 2002, refers to a damage bonus that is granted when certain like-type creatures engage in combat under the control of a single Tamer. It recognizes that certain animals fight far more efficiently as a team than when solo. There are seven types of pack instinct creatures: Pack TypeCreatures ArachnidFrost Spider, Giant Spider, Scorpion, Wolf Spider BearBlack Bear, Brown Bear, Grizzly Bear, Polar Bear BullBull CanineDire Wolf, Dog, Grey Wolf, Hell Hound, Timber Wolf, White Wolf DaemonFire Steed, Imp EquineFire Steed FelineCat, Cougar, Hellcat, Leader Hellcat, Panther, Predator Hellcat, Snow Leopard OstardDesert Ostard, Forest Ostard, Frenzied Ostard As suggested above, a Frost Spider and a Giant Spider both belong to the Arachnid group and can be used together to receive the pack instinct damage bonus. However, while a Frost Spider and Black Bear both can use pack instinct, they do not receive the damage bonus when used together since one is of the Arachnid group and the other is of the Bear group. Pets in PackDamage Bonus 2+25% 3+50% 4+75% 5+100% Notes All of the pets within the pack must be engaged with the same target to receive the maximum damage bonus. For example, if your 5-pack team engages two targets, with 3 pets on one target and 2 on the other, then you will only receive a total damage increase of +75%. The group of 3 garner a +50% bonus and the group of 2 receive a +25% bonus.[1] Pack Instinct is of particular value to Animal Tamers that are still mastering their skill. It allows them to hunt creatures that would otherwise handily dispatch the creatures that are subject to lower levels of Animal Taming skill. Put simply, Pack Instinct allows a Tamer to hunt bigger monsters, sooner. Neither the Dread Spider nor the Giant Black Widow are tamable, and therefore have no pack instinct. The Fire Steed, Imp, and Leader Hell Hound require 2 animal control slots.
