Lord Sutcliffe

Mentor

At the start of your turn, if Sutcliffe is face-down in your arsenal, you may turn him face-up.

While Sutcliffe is face-up in arsenal, whenever you play a non-attack action card, deal 1 arcane damage to each hero and put a lesson counter on Sutcliffe for each damage dealt this way. Then if there are 3 or more lesson counters on Sutcliffe, banish him, search your deck for a specialization card, put it face-up into your arsenal, and shuffle.

Rulings

From the Monarch release notes

Mentors do not have a pitch value or cost and cannot be pitched or played.
Mentors have their effect active when they are face up in your arsenal.
You cannot arsenal a card if there is not an empty arsenal zone.
You do not have to find a specialization card from your deck, you may elect to not find a card. This is because it is looking for a specific type of card and it is a hidden zone. You still must shuffle your deck.
Lord Sutcliffe does arcane damage to all heroes, not just opposing.
The turn player decides the order of replacement effects that would apply first. For example, if both players have arcane barrier, the turn player decides which replacement effect applies first and therefore who has to decide to prevent first.
The triggered ability is not once per turn, if you play multiple non-attack action cards it would trigger each time.