The freerunning mechanic, in particular, offers a variety of effects at a steeply discounted price that makes the cards adequate for Modern play
Probably the best matchup I could ask for: traditional Esper Dragons
When we are losing a matchup before sideboarding, its extremely important to identify why we are losing these games
And mechanically speaking, that shows up beautifully here as his static ability doubles all damage he would deal, and at the beginning of each end step, if he dealt damage to another Creature that turn, he gets a +1/+1 counter
Since youre gaining life while your opponents are losing life, Gray Merchant lets you pick and choose which of Astarions abilities you want to trigger at the end of your turn, either putting your opponents in a precarious situation, or helping you take the lead with a massive surge of health