Bridge Seed was the 8th card revealed for Beta 13.4 on Twitter. Previous Versions can be found here. It got a little change between reveal and release, but it was only a rewording in the dscription. This is because the old description made it look it like it didn't count itself.
Bridge Seed works as an alternative Dummy with Taunt, 0 ATK, but a lower base HP in exchange for the ability to draw cards. It also costs +1G. When you place it, it will already gain +1 HP and you will draw a card, leaving it with 0/3.
However, this effect will be triggered again for each Bridge Seed you have on the board. Here's a chart that shows all the outcomes:
1st: 0/3 + 1 card
2nd: 0/4 + 2 cards (same stats as Dummy)
3rd: 0/5 + 3 cards
4th: 0/6 + 4 cards
The last one is only able if you used cloning cards like Cloning or Echo Flower, as you are unable to have more than 3 in your deck.
To match with Undertale, when you have 4 Bridge Seeds on the board, they all sprout.