Does War Caster 5e feat in dnd let you use a cantrip using its full harm as your opportunity strike? Does it look too OP, especially at higher levels?

War caster 5e feat in dnd prerequisite: The ability to cast at a Minimum of One spell. You’ve practiced casting spells amid combat, learning techniques that grant you the following advantages:

1. You have an edge on Constitution saving throws that you make to keep your concentration on a spell once you take damage.
2. Every time a hostile creature’s movement provokes an opportunity attack from you, you can use your reaction to cast a spell in the creature, rather than making an opportunity assault.
3. Suppose you possess weapons or a shield in one or both hands. In that case, you may perform the somatic components of spells. 

It might seem like a cantrip as long as it fulfils the above requirements. That makes cantrips possibly a more appealing option than weapon attacks. Still, that’s part of the planned purpose of the feat.

Extra attack class feature

In terms of why there isn’t a similar feat for baseball strikes, keep in mind the extra attack class feature especially says “if you choose the Attack action.” A reaction is not that. You may, and it is more powerful, but you are investing a feat to get it done, so it makes sense. Additionally, remember that the target is still within your melee range when taking an Opportunity attack, so you would have a drawback in the attack roll if you use a ranged spell. 

Since you’re making an opportunity attack before they leave your achieve (which I presume is 5 feet), you’ll have a disadvantage on all ranged attack rolls. So EB is not all that lucrative. Instead of EB, you may use booming blade 5e or green flame blade. Both scale with the total amount so you can deal quite a bit of harm. And you’ll be able to use great weapon fighting it too.

When casting a spell for a reaction employing the War Caster feat in 5e, does this use up a spell slot?

When a hostile creature’s motion provokes an opportunity assault from you, you may use your reaction to cast a spell in the creature rather than making an opportunity attack.

Nothing is mentioned regarding slots’ usage when casting a spell as a reaction throughout the 5e War Caster feat. So is that a free spell, or does this fall through straight back to the standard spellcasting rules, which would require the usual expenditure of a slot?

Yes if you use a flat one or more significant spell, nevertheless Cantrips also classify as spells. However, they are considered level 0 that don’t expend spell slots.

So you can cast a Shocking Grasp by way of instance, or another cantrip you want! Should you use a level 1 or higher spell then yes, you have to expend the proper spell slot.

The text also does not clarify if there are limitations on the type of action that the spell requires so you can use any kind, be it Reaction, Bonus Action, 1 Action and all those without or with concentration to maintain (like the Hold Person spell by way of instance, which is preserved for a moment with concentration).

What is the possibility of a 5e War Caster Feat to cast an Opportunity Attack after a Bonus Action spell?

Bonus Action: A spell cast with a bonus action is incredibly swift. It would be best if you used a bonus action on your turn to cast the spell, assuming you haven’t already taken a bonus action this turn. You can’t cast another spell during precisely the same turn, except to get a cantrip using a casting time of 1 action. [PHB:203]

You cannot use Bonus Action out of your turn. Thus you are not bound by the rule.

On your turn

A possible situation:

The enemy fails its WIS rescue and provokes your Opportunity Attack.

If you use your reaction to cast a spell other than cantrip, you cannot cast Bonus Action spell, because it is still on your turn. But if you cast a cantrip instead, it’s still true that you can cast Bonus Action spell.

As the scenario in your query happens on your turn, the solution is yes. You’ll get a challenge from casting a Bonus Action spell if you cast a spell aside from cantrip using your reaction. You, however, aren’t prevented from doing this on your next turn.

A reaction can happen in anyone’s turn, including your turn, it is not outside the window of your switch and your next turn.

Can you combine War Caster 5e, whip, and Warlock Features to Eldritch Blast foes within Reach?

It is quite possible; however, Improved Pact Weapon isn’t necessary. You can earn an opportunity to attack a hostile creature that you can see moves out of your Reach every time.

Suppose you got the 5e War Caster feat when an enemy accomplishes an opportunity assault from you because of motion. In that case, you can forego the opportunity attack and instead use your reaction to cast a qualified spell-like eldritch blast.

As discussed above, the principles on War Caster in 5e says the following. Every time a hostile creature’s movement provokes an opportunity assault from you, you can use your reaction to cast a spell at the creature, rather than making an opportunity assault.

So, yes, your intended strategy works. The enemy provokes an opportunity attack because of movement. Rather than creating an opportunity attack, you utilize your reaction to cast eldritch blast.

But it is entirely irrelevant whether the whip is your spellcasting attention or not. With Improved Pact Weapon, you could offer your pact weapon’s material components because of your attention. Still, the eldritch blast does not have material components, so Improved Pact Weapon is unnecessary to earn this tactic work. All you will need is the War Caster feat & a 5e whip.

Combining Warlock War caster & Polearm in 5e

But they could still wield them—just kind of horribly. Nevertheless, there’s an interesting usage of the Polearm Master feat and the 5e War caster cantrip feat. The Polearm Master feat lets you perform an opportunity attack against anybody that enters the melee range. War caster permits you to cast a spell because of your reaction instead of making a melee attack.

By Level 5 (using a human variant), when you combine all three of those you have a type of a bubble around the warlock that makes it decidedly hard for anything to get within melee range as the minute anything gets inside melee range you can burst it back twenty feet (presuming you create either your rolls). You will perform an average of a bit under 20 damage every time. When it’s an ancient red dragon or your friend frank, so long as you join it’ll return 10 feet each column.

Power Word: Kill

Granted you can only do this once per round, and it absorbs your action (and two feats!), Keeping selected enemies out of melee can be tremendously beneficial to the celebration’s health and well-being. Further, you don’t need to cast a cantrip. You can just as quickly cast “Power Word: Kill” to the very first thing got in melee (assuming you were high enough level). Once per round you produce a trigger zone that activates any spell you need, at any level you like. It targets the creature that activates the trigger for the cost of two feats. A Warlock can make a polearm pact weapon, and he will be proficient in that.

Also, there are several confusions about War caster 5e. You may just cast a spell to the creature that triggered the OA. You can not change aims around. Like you can’t utilize a creature excite to assault another adjacent creature. Also, only enemies may excite OAs. Allies cannot do anything to provoke.

Does War Caster 5e feat in dnd let you use a cantrip using its full harm as your opportunity strike? Does it look too OP, especially at higher levels?

War caster 5e feat in dnd prerequisite: The ability to cast at a Minimum of One spell. You’ve practiced casting spells amid combat, learning techniques that grant you the following advantages:

1. You have an edge on Constitution saving throws that you make to keep your concentration on a spell once you take damage.
2. Every time a hostile creature’s movement provokes an opportunity attack from you, you can use your reaction to cast a spell in the creature, rather than making an opportunity assault.
3. Suppose you possess weapons or a shield in one or both hands. In that case, you may perform the somatic components of spells. 

It might seem like a cantrip as long as it fulfils the above requirements. That makes cantrips possibly a more appealing option than weapon attacks. Still, that’s part of the planned purpose of the feat.

Extra attack class feature

In terms of why there isn’t a similar feat for baseball strikes, keep in mind the extra attack class feature especially says “if you choose the Attack action.” A reaction is not that. You may, and it is more powerful, but you are investing a feat to get it done, so it makes sense. Additionally, remember that the target is still within your melee range when taking an Opportunity attack, so you would have a drawback in the attack roll if you use a ranged spell. 

Since you’re making an opportunity attack before they leave your achieve (which I presume is 5 feet), you’ll have a disadvantage on all ranged attack rolls. So EB is not all that lucrative. Instead of EB, you may use booming blade 5e or green flame blade. Both scale with the total amount so you can deal quite a bit of harm. And you’ll be able to use great weapon fighting it too.

When casting a spell for a reaction employing the War Caster feat in 5e, does this use up a spell slot?

When a hostile creature’s motion provokes an opportunity assault from you, you may use your reaction to cast a spell in the creature rather than making an opportunity attack.

Nothing is mentioned regarding slots’ usage when casting a spell as a reaction throughout the 5e War Caster feat. So is that a free spell, or does this fall through straight back to the standard spellcasting rules, which would require the usual expenditure of a slot?

Yes if you use a flat one or more significant spell, nevertheless Cantrips also classify as spells. However, they are considered level 0 that don’t expend spell slots.

So you can cast a Shocking Grasp by way of instance, or another cantrip you want! Should you use a level 1 or higher spell then yes, you have to expend the proper spell slot.

The text also does not clarify if there are limitations on the type of action that the spell requires so you can use any kind, be it Reaction, Bonus Action, 1 Action and all those without or with concentration to maintain (like the Hold Person spell by way of instance, which is preserved for a moment with concentration).

What is the possibility of a 5e War Caster Feat to cast an Opportunity Attack after a Bonus Action spell?

Bonus Action: A spell cast with a bonus action is incredibly swift. It would be best if you used a bonus action on your turn to cast the spell, assuming you haven’t already taken a bonus action this turn. You can’t cast another spell during precisely the same turn, except to get a cantrip using a casting time of 1 action. [PHB:203]

You cannot use Bonus Action out of your turn. Thus you are not bound by the rule.

On your turn

A possible situation:

The enemy fails its WIS rescue and provokes your Opportunity Attack.

If you use your reaction to cast a spell other than cantrip, you cannot cast Bonus Action spell, because it is still on your turn. But if you cast a cantrip instead, it’s still true that you can cast Bonus Action spell.

As the scenario in your query happens on your turn, the solution is yes. You’ll get a challenge from casting a Bonus Action spell if you cast a spell aside from cantrip using your reaction. You, however, aren’t prevented from doing this on your next turn.

A reaction can happen in anyone’s turn, including your turn, it is not outside the window of your switch and your next turn.

Can you combine War Caster 5e, whip, and Warlock Features to Eldritch Blast foes within Reach?

It is quite possible; however, Improved Pact Weapon isn’t necessary. You can earn an opportunity to attack a hostile creature that you can see moves out of your Reach every time.

Suppose you got the 5e War Caster feat when an enemy accomplishes an opportunity assault from you because of motion. In that case, you can forego the opportunity attack and instead use your reaction to cast a qualified spell-like eldritch blast.

As discussed above, the principles on War Caster in 5e says the following. Every time a hostile creature’s movement provokes an opportunity assault from you, you can use your reaction to cast a spell at the creature, rather than making an opportunity assault.

So, yes, your intended strategy works. The enemy provokes an opportunity attack because of movement. Rather than creating an opportunity attack, you utilize your reaction to cast eldritch blast.

But it is entirely irrelevant whether the whip is your spellcasting attention or not. With Improved Pact Weapon, you could offer your pact weapon’s material components because of your attention. Still, the eldritch blast does not have material components, so Improved Pact Weapon is unnecessary to earn this tactic work. All you will need is the War Caster feat & a 5e whip.

Combining Warlock War caster & Polearm in 5e

But they could still wield them—just kind of horribly. Nevertheless, there’s an interesting usage of the Polearm Master feat and the 5e War caster cantrip feat. The Polearm Master feat lets you perform an opportunity attack against anybody that enters the melee range. War caster permits you to cast a spell because of your reaction instead of making a melee attack.

By Level 5 (using a human variant), when you combine all three of those you have a type of a bubble around the warlock that makes it decidedly hard for anything to get within melee range as the minute anything gets inside melee range you can burst it back twenty feet (presuming you create either your rolls). You will perform an average of a bit under 20 damage every time. When it’s an ancient red dragon or your friend frank, so long as you join it’ll return 10 feet each column.

Power Word: Kill

Granted you can only do this once per round, and it absorbs your action (and two feats!), Keeping selected enemies out of melee can be tremendously beneficial to the celebration’s health and well-being. Further, you don’t need to cast a cantrip. You can just as quickly cast “Power Word: Kill” to the very first thing got in melee (assuming you were high enough level). Once per round you produce a trigger zone that activates any spell you need, at any level you like. It targets the creature that activates the trigger for the cost of two feats. A Warlock can make a polearm pact weapon, and he will be proficient in that.

Also, there are several confusions about War caster 5e. You may just cast a spell to the creature that triggered the OA. You can not change aims around. Like you can’t utilize a creature excite to assault another adjacent creature. Also, only enemies may excite OAs. Allies cannot do anything to provoke.