Here's my reasoning. On the map, a third-level neutral creature can certainly cause trouble (genies, water elementals, cyclops, ifrits for a fighter, etc.), but in the final battle, a Naga is definitely more dangerous than all of the above. Nagas are feared more than fourth-level creatures. Because the "teleport, then double attack on an area with wait" tactic is very, very dangerous. Taking down a bunch of heroes with a single unit is only possible for Imps, and even then, they don't stand a chance in most setups, while Nagas can do it without any problems.
Не стремясь приобщиться к основам пришёл.
В прошлый раз утащил я молитвенный коврик,
Он истерся до дыр, - я за новым пришёл.
© О. Хайям