Dialga & Palkia, perfected

Indestructible, trample, flying, islandwalk, plainswalk, mountainwalk, swampwalk, forestwalk, hexproof, lifelink,
At each upkeep, bolster 10
Dialga and Palkia's power is equal to your life total rounded up + 5
Dialga and Palkia's toughness is equal to your life total + 5
This can't be the target of spells and abilities your opponents control
This spell costs {1} less to cast for each legendary permanent in your graveyard