Splug was one of the many goblins recruited by Kalarel to harass the people of Winterhaven to keep them from investigating cultist activity at Shadowfell Keep. Splug attacked the main Acq Inc team as they began to venture into the keep, but after being cornered, convinced the party to spare him in return for leading them to the death cult.
Splug was left for dead in Shadowfell Keep as Omin Dran went to rescue Binwin Bronzebottom and ignored the dying Splug.
Reappearances in 'The C-Team' (spoilers)
The C Team's first official assignment was to put an end to goblin raids north of Westbridge. As they rode up the Stone Road, they came across multiple broken down carts, including a gothic-looking one with velvet-upholstered seats and cases of magic wands with the engraving 'Percival' on them (hinted to belong to Percival Darkmagic). The team repaired and took over the gothic cart but were soon accosted by a band of goblins who leaped out of their own wagon. The C Team quickly took them out, mostly thanks to Donaar's acid breath and some intimidation, and recovered the items that were stolen--including a dragonborn egg.
Later when they returned to town, the cart was attacked at night by wargs and masked goblins wearing black leather armor, trying to steal back the items. The C Team fought them off and returned to the Dran and Courtier Inn to find more goblins waiting for them. Splug was inside, richly dressed with "skin lightly scarred as if by flame, but with the care of a magical healer...you can tell there was a grievous injury in his past". He then advised the C Team, "Don't trust Acquisitions Incorporated. And certainly don't trust Omin Dran". He then left a card on the table that said 'care of Splugoth the Returned' with the symbol of 'The Six'.
While assigned to be security on a casino barge, the Team later ran into Spluggoth, who admitted, "I've got too much money". When Donaar was assigned to be his bodyguard, Splug revealed that in return for killing all those goblins, he had tattled to Skala that the C Team now had their egg. Splug also remarked that it was just a matter of time before Omin betrayed them, and that the game Omin plays "is not one other people can win". He detailed what Omin did to his boss, Jeff Nomagic, describing it as "cruelty; that's Omin Dran". Splug hinted that when Omin betrays Donaar, he'll be welcome to join the Six, even if he's killed (with Splug admitting that he himself has died "a couple of times...it's the coming back that hurts").
On later encounters with the Six, the C Team are often pursued by carts filled with goblins, presumably still under the command of Splugoth.
 Acquisitions Incorporated: Season One : Episode 1-8 (Splug is not named until episode 4)
 C Team S1E16 - Doomgate Inn - Part 2
 S1E17 - The House Wins Parts 2-3
 S3E29 - Crucible Part 5