Abilities » Bodyguard | Attacks » Poltergeist
Does Marowak's "Bodyguard" Ability prevent me from revealing my hand from an opponent's Trevenant's "Poltergeist" attack?
Yes, it does.
Source: TPCi Rules Team (2017-05-18)

Relevant cards

Note: All applicable cards may not be listed below.
SM2_7
XY10_37