Ren the Unclean is one of the more vicious of the Nazgul permanent-events, with his ability to force corruption checks upon every character in the game. He gets a run in many decks and only Uvatha the Horseman turns up more often. I'm not sure if Ren the Ringwraith will appear with equal regularity, but he possesses a special ability and an Unleashed short-event that make him an excellent consideration for certain resource and hazard strategies.
First, a look at Ren's stats. They are reasonable at 8/10, a low prowess and a high body. His direct influence is 4, allowing him to control many of the decent mid-range characters, like Ufthak. Even though he is a Diplomat, his changes little in Heralded Lord mode, increasing to 5 overall. In Fell Rider mode he becomes quite the warrior with 12 prowess. Odd, considering that he is not a Warrior.
He has the two skills considered least useful in regular characters, Sage and Diplomat. However, the normal assumptions do not apply to Ringwraiths. Having them sit in a Darkhaven to heighten the hand size, test rings or use special abilities is a valid strategy, and means that Warrior, Scout and Ranger are seldom required. Sage, on the other hand, enables Ren to play the important Voices of Malice card.
Ren can use two types of magic, the equal of Indur and the Witch-King and only bettered by the master mage himself, Akhorahil. Ren's magics are Shadow and Sorcery, so he has access to most of the powerful cards, A Malady Without Healing, Freeze the Flesh, Gold Chains in the Wind, Veils of Shadow and Some Secret Art of Flame (which is better than any Warrior card).
Ren's real strength is his special ability and his Unleashed card. If at a Darkhaven, he can alleviate the burden of corruption from one of his companies. Unfortunately, the +2 does not help character's bearing un-tested Gold Ring Items, as the corruption check forced by these is at the end of the untap phase, before Ren can come to their aid. No matter, there are more items than these.
The strategy would appear to be to have just the one company whose goal is to gather major and greater items, with Ren back at the Ranch willing his minions not to stray from Sauron's path. Tapping Ren each turn allows a character to have up to 6 CP and still require snake-eyes to visit the discard pile. The worst characters with 5 CP (say, the High Helm and Mithril-Coat - ouch, that's nasty) can expect is to tap. This is restrictive, as Ren cannot also gallivant around to other sites find neat stuff, summoning war hosts or frustrating the opponent. However, he can still be used as a card generator, moving between Darkhavens each turn (even tapped the Ringwraiths fear little, and he can still use magics to defend himself).
The other Ren strategy comes from the Ren Unleashed card. This forces corruption checks upon all characters at the same site as Ren. Nice. But the checks are at -2. Evil. With an opponent playing with minion companies, this may not be overly destructive.
But pit Ren against a Wizard opponent and he really is unleashed. Forcing corruption checks at -2 poses a real threat even to characters with one Lure or a major item. Both of these and a six or lower sends our hero packing. As a Wizard, unless I was following a faction or mission strategy, the site of Ren on the table would be cause for serious concern.
There is no one best Ringwraith and there are no Ringwraith failures. Each has its place in supporting a particular strategy for victory. Ren's best terrain is as clearly marked as that of any Ringwraith.
Original card review taken from : http://fan.theonering.net/morgulrats/
With the authorization of the webmaster.
The reviewing team consisted of Gwaihir (Chris Farrell), Gimli (Nathan Bruinooge), Ohtar (Charles E. Bouldin, Esq.), Radagast (James Kight), Joshua B. Grace (Beorn), Martijn Steultjens (Fram Frumgarson), Jason Klank (Saruman) and Jeffery Dobberpuhl (Wormtongue)