When a creature with double strike and trample deals combat damage in Magic: The Gathering, it first assigns damage equal to its power to the defending creature or player. Any excess damage is then assigned to the defending player or planeswalker. This means that the trample ability can be used to deal additional damage to the defending player or planeswalker after the defending creature has been dealt lethal damage.
The official ruling on interactions involving Teysa Karlov in Magic: The Gathering is that her ability doubles triggered abilities of creatures dying. This means that when a creature dies, any abilities triggered by its death will trigger twice if Teysa Karlov is on the battlefield.
The official ruling on Phyrexian Obliterator in Magic: The Gathering is that when it is dealt damage, that damage must be paid in the form of permanents being sacrificed.
The official ruling on Nivmagus Elemental in Magic: The Gathering is that it can exile instant and sorcery spells you cast to grow stronger, but it cannot exile itself.
The official ruling on the use of "Wish" cards in Magic: The Gathering tournaments is that players are allowed to use them, but they must adhere to the tournament rules and guidelines set by the event organizers.
The official ruling on the Nexus of Fate card in the current Magic: The Gathering tournament format is that it is banned in Standard and Historic formats, but legal in other formats like Commander.
Ajani's Pridemate is a card in Magic: The Gathering that gains 1/1 counters whenever you gain life. Its official ruling is that it triggers whenever you gain life, even if you gain multiple life points at once. This interaction can be powerful when paired with cards that allow you to gain life consistently.
As of the current Magic: The Gathering rules, Cathars' Crusade is a legal card that can be played in the game. It is not banned or restricted in any format.
Commerce power to include all commercial interactions
Yes
As of the latest Magic: The Gathering set, Omnath, Locus of Creation has been banned in Standard format due to its powerful and dominating presence in the game.
Yes, new evidence can potentially overturn a double jeopardy ruling if it meets certain legal criteria and is deemed significant enough to warrant a retrial.
In the Commander format of Magic: The Gathering, Rat Colony is allowed to have any number of copies in a deck, as long as the deck contains only one copy of each card (excluding basic lands). This ruling was made by the official rules committee for the Commander format.