i want to find out if Thengel is really OP.

undoubtly he is a good hero, with great stats and an ability that have much potential. but is he better than a Gandalf, an Elrond, Dáin Ironfoot or Círdan the Shipwright?

i made 3 decks where i found he makes nearly the most out of his ability and then i want to compare that with classical high end. what means compare? it is not easy to compare, because the abilities need circumstances like Vilya ore dwarfes..... overall i think the get "discard an ally from play" is harder to achieve than having #vilya in play or dwarfes, or To the Sea, to the Sea!, but it is usable without any more costs (exhausting elrond, discard cards,....)

in this cases i would say he is at best equal to all that toptier-heroes. so, when he can become op? only together with other toptier heroes, and thats what the 3 decks i made want to investigate.

the choice of the allies is very limited. mot as limited as it is for Dáin Ironfoot but the only allies with discardabilities are creatures and rohan. yes with beornings you can also do nice things, but this would only result in a battleheavydeck, that can be usefull in multiplayer, but in solo it is far away from op. the other decks:

• https://ringsdb.com/decklist/view/38465/isthengelopelrondmotk-gildor-1.0
• https://ringsdb.com/decklist/view/38469/isthengelopthedendenethorrohan-1.0

this deck:

the 3rd way i can imagine Thengel is OP is with Radagast

it is quite similar to the rohandeck, the additional discount comes from Radagast + his Radagast's Staff. in addition to that, with the Wizard Pipe (perhaps included by Bilbo Baggins) you can adjust what you will find with Thengel

with staff and Steward of Gondor you can buy for 7 res and change a 1 cost ally for 4-5 cost, so worth of 11-12 res within a round multiple times.

to get the things you need the A Fair Exchange and Word of Command helps, so it is not unlikely to get the high amount running.

compare to the rohanversion you have istari-shenanigans (pipe word of comand). compare to the vilyaversion you have sneack and option to faramir. (sneack not only good with Gandalf also good with Meneldor

mulligan: staff and steward, word

conclusion:

generally spoken, it scratches the edge of OP-ness. A Fair Exchange finally flipps it over the boarder, thengels part of the put into play res is about 30-40% (the discarded ally costs himself). perhaps with some Giant Bear it could even be improved.