defeating turtle

[easytarget]

ok, couple follow on questions

what is this portal you speak of? something i assume i've not run into yet at the stage of the game i'm at, because it would be handy to be able to bring in additional support during a battle (assuming that's what you mean)

and second, does that mean, sometimes you can use rage on bosses and sometimes you can't, just depends on the boss? and if it's a sometimes can sometimes can't thing, is it random like the drops, or when players encounter the turtle do they always not get to use rage?