I'm playing Modern U/G Infect (example list). I need help dealing with Gideon of the Trials and Gideon, Ally of Zendikar. The first Gideon's emblem means I need to attack twice to win, and his +1 ability also stops me from doing damage if I have only a single infector out. The second Gideon keeps the first Gideon's emblem active, plus makes an endless stream of blockers for my attackers. What can I do about these cards?
I'd say your best bet is to ignore it. Gideon of the Trials is not a common card in Modern, and with the format as wide as it is, dedicating sideboard slots to combating this rare threat is not a good idea. If you can't ignore Gideon (maybe there's someone who consistently plays Gideon tribal at your local store), then these cards might help:
- Echoing Truth is a catch-all against every hate card, from Gideon to Chalice of the Void on 1.
- Spell Pierce can stop Gideon from resolving in the first place, which is probably your best bet, since killing Gideon after it's entered play will be very hard. Spell Pierce also interacts with Path to Exile (which any deck playing Gideon is likely to have). Infect is fast enough that the opponent is not likely to get to five mana to pay for it.
- Sorcerous Spyglass is the next card that comes to mind. As long as you cast Spyglass before Gideon enters play, he does nothing.
There are some common sideboard cards that are effective here.
Spell Pierce can keep Gideons off the field for just 1 mana. Gideons cost a lot of mana (for modern), so they should rarely be able to pay. It can also deal with removal and nasty sideboard cards like Solemnity
Echoing Truth can help manage a resolved Gideon. It can remove a Gideon from the field to turn off his emblem and can remove all the Knight Ally tokens at once (though note that both Inkmoth Nexus and Blighted Agent go around them anyways). It can also handle infect hosers like Solemnity or Melira.
Spellskite is probably the best way to deal with Gideon of the Trials's +1. It also deals with Path to Exile, a common sight in decks that play Gideon.