It means you can risk playing ramp spells or do nothing permanents on-curve
Theres nothing stopping you from proxying Ersta, Friend to All or The Cinematic Phoenix in a casual setting, if your playgroup allows it
There's really not much to say about it, the design is simple yet powerful and, above all, it clearly synergizes with what I've been looking for in every warp card since the beginning of the article: enter the battlefield effects
If you're using Sword of Hearth and Home, you can also flicker your Knight for yet another land if someone else is ramping hard
If Grimgrin's last ability resolves, but the targeted creature isn't destroyed (perhaps because it regenerated or has indestructible), you'll still put a +1/+1 on Grimgrin
As long as any copy of Pack Rat remains alive, this game pattern will continue and ultimate take the game