All the rules for adding them to your game are included in the box.

The Tsang Tribe

This is the original Tcho-Tcho faction as portrayed by Petersen Games. It does include all the balance changes. Their tactics and tricks are unchanged, save for the fact that your opponents do not know who you are.

The Leng Tribe

The Leng tribe has some nasty surprises up their sleeves. Unlike Tsang, you have no unique movement ability, but you need to move your strategy, so you have to use your multiplicity of high priests to get enough power for those moves.

Surprise! an action costing 2 Power. An enemy player has to choose one of their acolytes, and swap it out for one of your Proto-Shoggoths.

Dark Rituals Use it once per turn. When you play it, each enemy player with one of your High Priests in their Starting Area has to choose whether to pay you 2 Power or 2 Doom. (A player with less than 2 Power or Doom is immune.)

Fulmination A one-time post-battle effect. If Ubbo-Sathla was killed in the Battle, you can discard him out of the game permanently, and gain 1 Elder Sign for each unit killed in the battle (on both sides).

The Sarcomand Tribe

This is the first faction - well, sub-faction - specifically designed to work with independents and neutrals. Clearly your free Great Old One is an important decision. As with the Leng tribe, you paint a movement ability. While you will not require as much movement as ling, you need power for summoning and rituals, so your free extra high priests come in quite handy.

Otherworld Alliances this adds 1 to the Combat of all your Neutral Monsters and Terrors.

Doomsday another one-use spellbook. When you take it, you immediately pick any Independent Great Old One with a cost of 2 or 4 (only) and place it at your controlled Gate. Always fun.

Inerrant when you Ritual, gain 1 Elder Sign for each enemy-controlled Gate at which you have any Great Old Ones.