As an additional cost to cast this spell, sacrifice a creature. Look at the top X cards of your library, where X is the sacrificed creature's power. Put one of those cards into your hand and the rest into your graveyard.
Primal {1}{W}{W}(During your turn, you may cast this spell for {1}{W}{W} instead of playing a land.) Return target creature card from your graveyard to the battlefield.
Target creature gets +2/+2 and gains lifelink until end of turn. Whenever that creature perseveres this turn, target opponent loses 2 life. (A creature perseveres when it survives damage.)
Primal {1}{G}{G}(During your turn, you may cast this spell for {1}{G}{G} instead of playing a land.) When Swampedge Sentinel dies, return another creature card from your graveyard to your hand.
Starting with you, each player may sacrifice a creature. Each player that doesn't loses life equal to the total power of creatures sacrificed this way.