I got a "You are about to enter arena" message when I saw someone already summoning pet in there. Then I did get ported in and joined fighting and killing Swelter pet, which i do not have.
[10:25] New Quest: "Beasts of the Pit"
[10:25] Shield of the Risen no longer protects you
[10:25] [Global] [Zummigummi]: is it chosain tiger is sold?
[10:25] [Global] [Darkgemli]: LFM vistrix 1 tank 3 healers 5 dps 2 mage
[10:25] [Global] [Lehyan]: lfm flame vortex palace hm full aa exp decent gear
[10:26] You are about to enter the Arena.
[10:26] [Global] [Auredicta]: Anyone for t2?
[10:26] [Global] [Darkgemli]: LFM vistrix 3 healers 5 dps 2 mage
[10:26] Vlavia, Blessed Warrior
[10:26] vs.
[10:26] Swelter
[10:26] You have 30 seconds to summon your opponent.
[10:26] Dimchik, Godslayer
[10:26] vs.
[10:26] Swelter
Here is a screen:
http://i68.tinypic.com/2i0aov8.jpg