Thekal comes with 2 named humanoid adds and 2 tigers. The 2 humanoid adds are a shaman and a rogue. Thekal initiates the fight in priest form, where he can mortal strike. If any of the adds or Thekal dies, the remaining ones will resurrect them. This means all 3 must die simultaneously.
After dying once, Thekal respawns as a Tiger. In this form he can charge, flurry, enrage, and Force Punch. Force Punch is an AoE attack around Thekal that does ~1000 damage. He often does it twice in a row. Furthermore he spawns 2 tigers periodically throughout the fight.
Tiger Form
In Tiger Form, Thekal gains a new set of abilities (listed below). He will periodically spawn two elite tigers which need to be taken down as quickly as possible. The tigers are capable of killing healers in a few hits, but do not have many hit points themselves.
Like Panther, phase 2 cannot drag on longer than two or three minutes or else the healers will likely be tapped both from healing the main tank and the damage caused by the tiger spawns. Thekal has relatively low HP and armor in this stage, so heavy DPS is a must.
The main ability the entire raid group needs to watch out for is Thekal's Force Punch. Between phases 1 and 2, the entire raid except for the main tank should run to the hill near Thekal's hut with their backs to the wall. Trying to outrange the AoE is not recommended--the range is large enough that if you are avoiding it, you're also not in range of being able to do anything.