Shelly, Hardened Traveler (Yellow)

Action -

: Attack

Instant -

: The next attack action card you defend with this turn gets +1

.

Watery Grave

After you resolve Shelly’s instant activated ability, the next attack action card you defend with this turn gets +1. This includes situations where the next attack action card you defend with is one that was added to the combat chain by an effect (e.g. Pulsewave Harpoon).

Watery Grave - When this is put into your graveyard from the arena, turn it face-down.

Watery Grave is an ability keyword.
Watery Grave is a trigger that ONLY triggers if the card is put from the arena into the graveyard, excluding when it is a non-permanent defending card on the combat chain. It also does not trigger if it is put into the graveyard by other means (e.g. discarded from your hand, destroyed from the top of the deck, put into the graveyard from your deck).
When Watery Grave’s triggered effect resolves, you must turn that card with watery grave face-down in your graveyard.
Similar to face-down cards in the banish zone, you can look at face-down cards in your graveyard. Opponents cannot look at face-down cards in your graveyard.
Cards and effects that interact with cards in the graveyard cannot interact with face-down cards in the graveyard unless the effect specifies that it affects face-down cards. For example, if a card requires you to banish 3 random cards from your graveyard as an additional cost, face-down banished cards are unable to be banished from your graveyard this way to pay for the cost.

Cost2

Attack4

Life5