Learn German: Er redet, als ob er der Meister wäre. - He talks as if he were the master.

The phrase als ob (as if) sets up an irreal comparison—a situation that isn't actually true. Because he isn't really the master, German uses the Konjunktiv II form wäre (were/would be) instead of the regular present tense ist (is).

Why is the verb wäre at the very end of the sentence?

The phrase als ob acts as a subordinating conjunction. Just like weil or dass, it creates a subordinate clause and kicks the conjugated verb (wäre) all the way to the end of that clause.

Could I say this without using the word ob?

Yes, you can use just als instead of als ob, but it changes the word order. If you drop the ob, the conjugated verb jumps to the position right after als, like this: Er redet, als wäre er der Meister.

Why is it der Meister (nominative) instead of den Meister (accusative)?

The verb sein (which wäre comes from) is a linking verb. It acts like an equals sign between the subject (er) and the noun describing him. Because the subject is in the nominative case, the matching noun (der Meister) must also take the nominative case.