cards with descend mtg set:lci o:descended · Scryfall Magic: The Gathering Search Delirium Put a 4/4 white Angel creature token with flying onto the battlefield if there are four or more card types among cards in your graveyard. Darkness Descends | Lorwyn Eclipsed

So investigate never sits on the stack by itself, and you cant respond to just investigate happening you can only respond to the spell or ability that tells you to do it

Now Faithless Looting was cheap enough that it became a powerhouse, whereas this is just three mana the first time and four the second

They have not just a higher density of spells in their pool of playables but those spells are also better suited to supporting Mentor in an attacking role

Return all nontoken creatures to their owners' hands

The Saproling tokens aren't created until after Fists of Ironwood is on the battlefield, so you can't cast Fists of Ironwood on one of those tokens

Yes MTG Agents is a purpose-built AI bot for MTG