Blurg is a Hobgoblin you can meet in both Act 1 and Act 3 of Baldur's Gate 3. He is a both a merchant and member of the Society of Brilliance, and he has some great items to trade with you as well as quests. So here is how to find him in both Act 1 and Act 3.
Act 1 Blurg location in Baldur's Gate 3 (Map)
Blurg can be found in the Myconid Colony, to the northeast of the Sovereign (X: 117, Y: -87). Not only is this Hobgoblin a friendly trader, he and his mindflayer friend will also will have a quest chain for you.
Act 3 Blurg location in Baldur's Gate 3 with Map
In Act 3, you can find Blurg in the Lower City in The Lodge (X: -202, Y: -82). This is the Society of Brilliance's headquarters. Depending on your choices in Act 1 and Act 2, Blurg might be dead or missing. He can be found on the upper floor of The Lodge in the library area if he is still around.
If you want to avoid getting Blurg killed, do not give Lady Esther the Gith egg; the Society of Brilliance ends up abusing the Githyanki child so badly, he kills everyone in the building. Either avoid Lady Esther entirely, or give her the Owl Bear Egg in order for Blurg to avoid this fate.
For more Baldur's Gate 3, check out How to get the Gemini Gloves in BG3 on Pro Game Guides.