What minions remain from original Battlegrounds other than Mama Bear, Goldrinn, the 1 mana 1/2 mech annoyotron and Wrath Weaver?
I can’t think of any minion that hasn’t been removed/adjusted
You can use this site
https://hearthstone.fandom.com/wiki/Battlegrounds/Minion
I created this query under
https://hearthstone.fandom.com/wiki/Special:RunQuery/CardChange
Mode: Battlegrounds
From Date: 2019-01-01
Number of results (I put 2000 just to make sure I got full history).
Battlegrounds was introduced in patch 15.6 so you can literally see every single minion (and hero) since day 1. If you care to do so.
In addition to the two you name it looks like Ghastcoiler and Kangor’s Apprentice are the only ones I can see were in the original 15.6 launch. There are a bunch that came in the 16.X patches but if you are truly talking OG from day one it looks like 6 total, some of which have been modified slightly in patches.
Baron and Brann are O.G. aren’t they?
Took a bit of work to dig it up, but Brann yes, Rivendare no.
Baron Rivendare (O.G.) and Titus Rivendare (current card) aren’t the same in name or functionality, so I think in the spirit of the OP’s question, I would say it doesn’t count.
I downloaded the entire repository of cards from patch 15.6 from Github in XML and used Excel to filter to what I believe are the original 69 battlegrounds cards.
The only minions that exist today (in some form) are Brann, Ghastcoiler, Kangor’s Apprentice, Wrath Weaver, Goldrinn, and Mama Bear. That’s it.
Edit: in patch 16 (which is the first major BG patch post release) the following were added:
Coldlight Seer, Floating Watcher
Baron was tweaked so they added his first name so they could claim they were adding a card.
It was also functionally changed. It wasn’t just a name change. Old - deathrattles trigger twice. New - deathrattles trigger an extra time. The current situation with beasts in BG is exacerbated by this.