Both of these can also be considered a top 10 card for collectors, also demanding a rather mighty price at around $72.13 for the former, and $232.71 for the later in the market right now
For a low cost to play and move characters, even if it gets removed it will likely mean a character survives instead
Kona, Rescue Beastie is a great card for the Commander and Pioneer formats, using mechanics like Convoke to gain the most value from the Beast Survivor
Finally, the Gravemother itself also has Encore, meaning that this card represents more value than it may appear to
Unlike Boros Reckoner this is a card you would play in red decks or white decks as well as the pure Boros
A 3/3 for three is okay, and it works like Vitu-Ghazi Guildmage with some tokens around, populating for three mana