Note that Umôrdhoth doesn't have the Monster trait, so it will not take increased damage from Lita Chantler.
Note that the action ability here is not a Parley, so you will get hit by an attack of opportunity when using it, and your investigator can be defeated before that action resolves.
- If an enemy is “considered” engaged with you because of the Massive keyword, it will enable abilities – like the Machete’s – that require you to be engaged with an enemy. However, there is no timing point of engagement, you’re just “considered” engaged with it, so you can’t really trigger reactions to becoming engaged with the enemy, like Zoey Samaras or Zoey's Cross.
The Devourer Below
Ancient One. Elite.
Umôrdhoth gets +4 health per investigator.
Forced - At the end of each investigator's turn: Ready Umôrdhoth.
If you control Lita Chantler: "It's only after her!" You throw Lita to Umôrdhoth in order to spare your lives. (→R3)
The FAQ provide a good explanation of why this last scenario is usually not much loved. Basically almost anything that you could try to shorten the massive amount of beating that the investigators stand to receive (3 damages and 3 horrors per each per round...) is disabled: no Lita,
no Machete, no Cross... (Edit: the Machete works, it was an error on my part. Of course it has been duly taboo-ed but against this enemy one is fully allowed to disregard the taboo list, in my opinion!)
So, not only you have a huge, huge enemy, which was expected: but all of your "smart ideas" are frustrated.
It may hammer the point home... But is not a lot of fun.