Unsettled Mariner
50PlayableCreature — Shapeshifter
Modern Horizons
2HG Rating
50/100
Plays about the same in 2HG as it does in any other format.
No 2HG-specific rules fire on this card — it plays much the same here as anywhere else.
Ratings start at a neutral 50 and are adjusted by rules derived from 2HG's structure — shared 60 life, shared turns, two opponents. They'll be recalibrated against real play rates once teams start submitting decklists.
Oracle text
Changeling (This card is every creature type.)
Whenever you or a permanent you control becomes the target of a spell or ability an opponent controls, counter that spell or ability unless its controller pays 
.
Legality
Plays well beside it
Fits the same colour identity — good candidates for your teammate's deck.
Suggestions are characteristic-based for now. Once teams submit pairings, this becomes a real co-occurrence score: played in X% of teams whose partner deck runs Unsettled Mariner.