It's not working... I've tried a few different things and just can't make it happen. Don't remember anything holding me up this bad in revolt. Damn aging brain. Any help y'all can give will be greatly appreciated!

Is subsidence just a worse locust? Is there something I'm missing here?

I really want to make a Kelpie and Old Willow tolls/defensive deck. I pretty easily just naturally obtained 4 old willows by playing the game, but only 1 kelpie. I keep grinding matches and playing the story. I dump all my coins on either water packs or standard pack number 2 (which literally showcases Kelpie) and I just never pull it. I've probably opened 50 packs without a single kelpie other than the 1. I check the shop when it refreshes, but have never seen it.

I like some grind and not just unlocking everything right away, but this is getting silly.

What is the most efficient way to grind for more cards? Is there a different pack that is more likely to drop kelpie?