Pets found on the last floor of Habitats

[Joshua]

Hello everyone,
I just cleared the last floor of the Fire Habitat and unlocked Devastor. This pet can be found in Gnarogrim. The problem is, since then I've been 3 times in Gnarogrim and...nothing. Does this mean that there is a chance to find this pet there (and not 100%, as it was with the other pets), or am I missing something? Thanks.
(Also, this could be clarified in the game manual/ in-game .)

[Gully]

Pets can be Normal, Rare or Epic.

Only the normal one have 100% drop rate

For rare and epic ones you might need way more that 1 go

[mar21]

Only guaranteed pets are these 1-time opportunity ones