Hold that three blue up to threaten an opponent during their turn, forcing them to cast something nonthreatening so they dont lose it to your counter, and then draw two cards at the end of their turn anyway
Hexproof only on your turn isnt as good as every turn, but its more than good enough, considering it stops interaction on big-swing turns
Selvala, Heart of the Wilds The most important resources in Magic are mana and cards, so any card that gives you an advantage in both regards becomes quite strong
All of the Dinosaur cards on this list boast rather intensive mana values
And being Colorless gives us the freedom to cherry-pick from some of the best Special Energies out there
The crazy part is that after all of that your opponent is behind because of Sinkhole and now they are further behind because of the extra turns you took building your board