You get to keep your blocker and wont take any damage unless the attacker has trample if you choose to block with River Boa and then regenerate it
With these cards there is no chance of buying a clipped Beta card, as long as you are familiar with what makes them unique

PSA Set Registry: Collecting the 2002 Pokmon Legendary Collection Set PSA Set Registry: Collecting the 2002 Pokmon Expedition Set - An "e-Xciting" and Overlooked Card Issue PSA Set Registry: Collecting the 2002 Pokmon Neo Destiny 1st Edition Set PSA Set Registry: Collecting the 2001 Pokmon Neo Revelation 1st Edition Set PSA Set Registry: Collecting the 2001 Pokmon Neo Discovery 1st Edition Set PSA Set Registry: Collecting the 2000 Pokmon Neo Genesis 1st Edition Set PSA Set Registry: Collecting the 2000 Pokmon Gym Challenge 1st Edition Card Set PSA Set Registry: Collecting the 2000 Pokmon Gym Heroes 1st Edition Card Set PSA Set Registry: Collecting the 1999 Pokmon Jungle 1st Edition Card Set PSA Set Registry: Collecting the 1999 Pokmon Fossil 1st Edition Card Set An Eye on the Prize: Collecting Pokemon Trophy Cards Collector Profile: Scott Pratte, Profiling a Premier Pokemon Trading Card Prognosticator PSA Set Registry: Collecting the 2000 Pokemon Team Rocket 1st Edition Card Set PSA Set Registry: Collecting the 1999 Pokmon 1st Edition Gaming Card Base Set, the Series that Started It All

Ive been somewhat unhappily keeping Damnation around in my Vintage Cube, and I intend to try this swap there
Rhystic Study, Trouble in Pairs, Sylvan Library, etc
The obvious choice is Ishai, Ojutai Dragonspeaker, but we'll talk more about Ishai later