Tarith, upon realizing the trap ahead, landed just outside it's bounds, trying to make it look like he was affected by the spell
bluff(1d20+21) or perform(something)(1d20+3)
He chooses to wait, and observe, planning on suprising any attacker with his capability to take action. While he is waiting, he focuses on the strange being, studying her with his arcane sight.
If you concentrate on a specific creature within 120 feet of you as a standard action, you can determine whether it has any spellcasting or spell-like abilities, whether these are arcane or divine (spell-like abilities register as arcane), and the strength of the most powerful spell or spell-like ability the creature currently has available for use.