Ere his fall were known...
Thematically, the idea of this deck is that Saruman is operating through the ents, while he works in the background using his doomed spells. Gríma is his emissary to the ents, and Éowyn is here (vaguely waving to Rohan's proximity to Isengard) for low threat and tactics access. (Note: Eowyn does not get the full value of her threat reduction in this deck since Saruman reduces any effect that reduces your threat to 1).
Strategy is pretty straightforward. Play lots of ents while using doomed events to ready Saruman, using him to both quest and attack. Getting Saruman's Staff out early is key to handle the threat increases, and since Saruman readies off playing a card with the Doomed keyword, he still readies even if the Doomed value is reduced to 0.
The ability to ready Saruman is particularly useful early in the game since Ents start out slowly - you can quest for 9 right off the bat and still ready Saruman as needed. Once the Ents are fully online, you can be more selective with the Doomed events to manage threat. The combination of Doomed events and Gríma's cost reduction also helps to get Ents moving faster. Treebeard can go in on turn one, Legacy of Númenor allows for some really fast starts (and is only Doomed 2 if you get the Staff out first), etc.
This deck doesn't contain any threat reduction since I tend to play it alongside my Silvan deck containing Galadriel and Galadriel's Handmaiden. If you need more threat reduction, you could swap out A Burning Brand (since Derndingle Warrior and Treebeard are key defenders) or one of the events like Boomed and Trumpeted or The Seeing-stone.