Probably an arcanist multiclass.
Spiderwalk, Create Pit, Invisibility (can cast non-targeting spells), Summon Elemental.
Spellcraft DC of the Create Pit was 17, 10 + ability modifier + spell level if it is still the same as 3.5e.
The weapons he carries seem to be leading to a multiclass, or just Exotic/Martial Weapon Proficiency.
Of course, he being a Summoner is also a possibility, considering his own words to the serpent-thing. But having an Eidolon with a Summon out together seems unlikely.