I observed two quirks with the battle selector (or however it's called). The feature when I right-click a monster, and it gets "locked", and I can use the Attack or the first seven combat-relevant items on it.
So if I knockback a monster into blackspace, it gets unlocked from the battle selector. Which is probably how it is intended to play. If the monster Blinks away, though, it seems to remain locked. Which is fine if it blinks around the discovered part of the map, but it seems to be the case even if it blinks into blackspace. Which leads to some weird interactions, pressing attack walks up to the monster and uncovers tiles.
On the Cursed Oasis (I'm sure this level is a dev's dream
), I can select a monster that exists in only one of the realms - say, a Shade - and have it remain selected even if I switch realms. Couple of exploits it allows are: kill a shade from normal realm and use Phys Res to do so; kill the Cursed Dragon despite having been thrust into the curse realm; pop a plant to get cursed again if it's selected. Interestingly, if I cast IMAWAL in the normal realm, when I have a curse realm plant selected, the wall will form in the tile but the plant will be pushed aside to the nearest empty tile (and IMAWAL will get partial cost refund as normal when cast on an empty space).
"Thinker", just without the "ache".