Is there a spell out there that can detect invisibility? So far I have Wyll in my party and I use the hunger spell to prevent him from going invisible which sort of helps with fighting him but would like to know if there are additional/better options to follow.
There is a See Invisibility spell as well as a magical eye from Volo and potions that grant See Invisibility. But they're not particularly great given that they don't work right and instead of seeing invisible things they just make invisible things roll a DEX save at the start of your turn if you're close enough to them...
The best ways to deal with invisibility are AoE effects. Notable are things like Create Water (Or throwing bottles of water), Spirit Guardians (Especially with any Radiant Orb generating items) and Sleet Storm.
Any AoE's will do, but things that hit a large area and always affect targets (I.e. No save to nullify them) work best.
I have also noticed that enemies tend to turn invisible at the end of their movement (not 100% but seems very common) giving you a clue where you can employ the AOE even if just a water bottle.
Also as has been mentioned positioning is very important in many fights. The AI will usually have significant advantage at the start, however you don't have to fight on ground of the AI's choosing. A tactical retreat/fighting withdrawal (not "flee combat") is almost always effective. You will find the AI will usually abandon good terrain in order to pursue you and close to melee range. As you retreat/withdraw you can wear them down with ranged attacks and slow them with AOE. You can usually withdraw/retreat to where the terrain is neutral or you have the terrain advantage (high ground, choke points etc). Not possible in all fights but it is in many.
Another effective strategy is to prioritize reducing enemy numbers quickly, I prefer to have party members concentrate fire on the same target whenever possible rather than having each of my party engage in 1vs1 battles. If outnumbered, gain parity ASAP, if you have parity. achieve superior numbers ASAP.
