Sacred Foundry, Inspiring Vantage, and Needleverge Pathway are twelve relatively free white sources (though playing a Pathway on white on Turn 1 can be rough in land-light hands), and then you even have Furycalm Snarl and Clifftop Retreat as additional multicolored lands if you want
Also, exiling half a players library is very strong since the cards never touch the graveyard, but at the same time there are diminishing returns in doing that each time you recast Ulamog, and are you really building in a milling alternate win con
We've all played against Jund, and had that feeling of games slipping away as Jund just does its thing
So in essence, Jaheira is treated both as a theme spell and a ramp spell, while only being 1 card out of the 99 rather than being 2 cards
If you run a red and blue deck, youll run both red and blue lands