Your options are mostly to draw The Eternal Wanderer (where you'll keep phasing the Forge out, and hope they don't draw a second copy) or hope you can overwhelm them with Virtue of Loyalty
The ideia was the same of the movie Highlander, where you can only have one, that's why you can only have 1 card of each in your deck
Kamahl, Heart of Krosa Kamahl, Heart of Krosa is a massive green commander that has quite interesting interactions
One-Off Utility Lands The Gold Saucer The Gold Saucer has a fabulously flavorful design that beautifully captures the idea of a city whose economy centers on gambling
The zombie Sliver has a mana cost of 3B with an ability that gives all Sliver creatures you control Afflict Two
Its going to be impossible to build around Duskmantle Seer for Sealed deck play, but a 4/4 flying creature for 4 that can "sort of" race is still tempting