The realization that one is dying is far more terrifying than death itself. Sidisi, Silumgar vizier Illustrated by Jack Wang Standard Not Legal Alchemy Not Legal Pioneer Legal Historic Legal Modern Legal Brawl Legal Legacy Legal Comp
Lands like Command Tower, Stomping Ground, Rootbound Crag, and Wooded Foothills ensure you have easy access to both colors, while Yavimaya, Cradle of Growth smooths out mana issues by making all lands into forests
That fact alone can make the card horribly frightening
A creature like Cold-Water Snapper has hexproof, while an enchantment like Leyline of Sanctity gives you hexproof
Now, obviously this can be taken too far
None of them seem likely to produce some obnoxious corner case interaction that takes over Legacy, so chalk that up as back-to-back wins for the Universes Beyond team