Boseiju, Who Endures

{T}: Add {G}.
Channel — {1}{G}, Discard Boseiju, Who Endures: Destroy target artifact, enchantment, or nonbasic land an opponent controls. That player may search their library for a land card with a basic land type, put it onto the battlefield, then shuffle. This ability costs {1} less to activate for each legendary creature you control.

Okina, Temple to the Grandfathers

{T}: Add {G}.
{G}, {T}: Target legendary creature gets +1/+1 until end of turn.

Eiganjo Castle

{T}: Add {W}.
{W}, {T}: Prevent the next 2 damage that would be dealt to target legendary creature this turn.

Mikokoro, Center of the Sea

{T}: Add {C}.
{2}, {T}: Each player draws a card.

Kethis, the Hidden Hand

Legendary spells you cast cost {1} less to cast.
Exile two legendary cards from your graveyard: Until end of turn, each legendary card in your graveyard gains "You may play this card from your graveyard."