The Ogler has 8 tentacles, and 8 spells, so you roll a (d8) to see what spell it casts.
Unless it's using 2 of its tentacles to fondle an adventurer, in which case you roll a (d6).
Or if it's using 4 of its tentacles on two adventurers, a (d4).
And the lower the roll, the deadlier the spell.