For XGG, Invasion of Ikoria lets you search your library and/or graveyard for a non-Human creature card with a mana value of X or less and put it onto the battlefield
Similarly, if a spell or ability forces you to sacrifice a creature, Umbra Armor can't step in there either
If you have 4 mana you can cast a ritual and splice a second one to get an extra mana for free
This applies to cards like Troll of Khazad-dm, which can be land-cycled to fetch for a land
But, the ability doesn't just limit this to creatures, so any other source of damage on your turn will be doubled
For players who look back at the first major One Piece TCG formats, OP01 Trafalgar Law is one of the leaders that helped prove the game had more depth than simply swinging with big numbers