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Whenever a creature enchanted by an Aura with umbra armor would be destroyed, you instead remove all damage and destroy the Aura, so targeted destroy-based removal spells are no longer a 2-for-1

There are so many cheap artifact spells that, even with only one turn to do it in, you could be quickly making a ton of Drone tokens

Should the opponent managed to stop the loop, the deck would ended up struggling to recover their disadvantagous position had they were not able to search and activate a copy of either "Welcome" or "Big Welcome"

Dedicated trade channels make it easy to connect

Force of Negation is no slouch in Commander, either, with nearly 350,000 decks running the card by EDHRECs current count