Return to Answer

I have this exact issue in a game I'm running (and the warlock can now fly, making him even more effective!). My strategies are still evolving, but I broadly have two categories I use to provide challenges for him: hard counters and soft counters.

Of those, I strongly prefer the soft counters.

###Soft Counters:

Soft counters are anything which frustrates or complicates the effectiveness of Eldritch Blast. The spell still exists, and would work well against enemies if the player can get around the obstacles, or would be a good idea if not for side effects. Examples of this include:

• The most important soft counter: smart tactics! Groups of enemies coordinating towards a common goal might succeed despite having a few members blown away by EB.
• Objects providing cover to enemies (bonus AC makes them harder to hit)
• Breaking line-of-sight (casting EB becomes impossible)
• Ancillary goals which are poorly served by EB (like the need to take people alive, or a need to interact with the environment which uses the Warlock's actions on other things)
• Opportunity costs. Your Warlock might be especially good at Eldritch Blast-ing, but they may also have spells, class features, or other options which are valuable (or crucial) to success. Setting up situations where there is a problem only a non-EB action from the Warlock can solve may make blasting less attractive (at times)
• Enemies/environmental hazards which impede spellcasting (such as frequently trying to grapple/restrain the Warlock)
• Enemies which are specialized to deal high damage to the Warlock, representing enemies' high priority on taking the Warlock out of the fight (high-damage snipers, for example)

###Hard Counters:

Hard counters are strategies which specifically neutralize or negate EB. I have fewer examples of these because I use them so sparingly-- they take away the fruit of a major investment this player made over other options:

• An antimagic field is going to short-circuit the EB-spamming strategy. Plentiful spell slots/spell-like abilities used to cast Silence or Counterspell can also frustrate your Warlock (credit to Renegade in comments for Silence and Counterspell)
• Enemies modified to be especially resistant to EB style attacks (they might have unreasonable AC, intended to be defeated by spells with saves)
• Enemies naturally resistant or immune to EB, like Helmed Horrors (credit to RonLugge in comments)
• Lingering effects. There aren't a ton of options to do this (thankfully), but enemies might start using abilities that reduce the Warlock's CHA stat, temporarily or permanently. I've not done this to the Warlock, but attribute penalties make for interesting situations every time I've encountered them.

I have this exact issue in a game I'm running (and the warlock can now fly, making him even more effective!). My strategies are still evolving, but I broadly have two categories I use to provide challenges for him: hard counters and soft counters.

Of those, I strongly prefer the soft counters.

Soft Counters:

Soft counters are anything which frustrates or complicates the effectiveness of Eldritch Blast. The spell still exists, and would work well against enemies if the player can get around the obstacles, or would be a good idea if not for side effects. Examples of this include:

• The most important soft counter: smart tactics! Groups of enemies coordinating towards a common goal might succeed despite having a few members blown away by EB.
• Objects providing cover to enemies (bonus AC makes them harder to hit)
• Breaking line-of-sight (casting EB becomes impossible)
• Ancillary goals which are poorly served by EB (like the need to take people alive, or a need to interact with the environment which uses the Warlock's actions on other things)
• Opportunity costs. Your Warlock might be especially good at Eldritch Blast-ing, but they may also have spells, class features, or other options which are valuable (or crucial) to success. Setting up situations where there is a problem only a non-EB action from the Warlock can solve may make blasting less attractive (at times)
• Enemies/environmental hazards which impede spellcasting (such as frequently trying to grapple/restrain the Warlock)
• Enemies which are specialized to deal high damage to the Warlock, representing enemies' high priority on taking the Warlock out of the fight (high-damage snipers, for example)

Hard Counters:

Hard counters are strategies which specifically neutralize or negate EB. I have fewer examples of these because I use them so sparingly-- they take away the fruit of a major investment this player made over other options:

• An antimagic field is going to short-circuit the EB-spamming strategy. Plentiful spell slots/spell-like abilities used to cast Silence or Counterspell can also frustrate your Warlock (credit to Renegade in comments for Silence and Counterspell)
• Enemies modified to be especially resistant to EB style attacks (they might have unreasonable AC, intended to be defeated by spells with saves)
• Enemies naturally resistant or immune to EB, like Helmed Horrors (credit to RonLugge in comments)
• Lingering effects. There aren't a ton of options to do this (thankfully), but enemies might start using abilities that reduce the Warlock's CHA stat, temporarily or permanently. I've not done this to the Warlock, but attribute penalties make for interesting situations every time I've encountered them.

I have this exact issue in a game I'm running (and the warlock can now fly, making him even more effective!). My strategies are still evolving, but I broadly have two categories I use to provide challenges for him: hard counters and soft counters.

Of those, I strongly prefer the soft counters.

###Soft Counters:

Soft counters are anything which frustrates or complicates the effectiveness of Eldritch Blast. The spell still exists, and would work well against enemies if the player can get around the obstacles, or would be a good idea if not for side effects. Examples of this include:

• The most important soft counter: smart tactics! Groups of enemies coordinating towards a common goal might succeed despite having a few members blown away by EB.
• Objects providing cover to enemies (bonus AC makes them harder to hit)
• Breaking line-of-sight (casting EB becomes impossible)
• Ancillary goals which are poorly served by EB (like the need to take people alive, or to preserve clothing or items while a solid EB hit might destroy them, or a need to interact with the environment which uses the Warlock's actions on other things)
• Opportunity costs. Your Warlock might be especially good at Eldritch Blast-ing, but they may also have spells, class features, or other options which are valuable (or crucial) to success. Setting up situations where there is a problem only a non-EB action from the Warlock can solve may make blasting less attractive (at times)
• Enemies/environmental hazards which impede spellcasting (such as frequently trying to grapple/restrain the Warlock)
• Enemies which are specialized to deal high damage to the Warlock, representing enemies' high priority on taking the Warlock out of the fight (high-damage snipers, for example)

###Hard Counters:

Hard counters are strategies which specifically neutralize or negate EB. I have fewer examples of these because I use them so sparingly-- they take away the fruit of a major investment this player made over other options:

• An antimagic field is going to short-circuit the EB-spamming strategy. Plentiful spell slots/spell-like abilities used to cast Silence or Counterspell can also frustrate your Warlock (credit to Renegade in comments for Silence and Counterspell)
• Enemies modified to be especially resistant to EB style attacks (they might have unreasonable AC, intended to be defeated by spells with saves)
• Enemies naturally resistant or immune to EB, like Helmed Horrors (credit to RonLugge in comments)
• Lingering effects. There aren't a ton of options to do this (thankfully), but enemies might start using abilities that reduce the Warlock's CHA stat, temporarily or permanently. I've not done this to the Warlock, but attribute penalties make for interesting situations every time I've encountered them.

I have this exact issue in a game I'm running (and the warlock can now fly, making him even more effective!). My strategies are still evolving, but I broadly have two categories I use to provide challenges for him: hard counters and soft counters.

Of those, I strongly prefer the soft counters.

###Soft Counters:

Soft counters are anything which frustrates or complicates the effectiveness of Eldritch Blast. The spell still exists, and would work well against enemies if the player can get around the obstacles, or would be a good idea if not for side effects. Examples of this include:

• The most important soft counter: smart tactics! Groups of enemies coordinating towards a common goal might succeed despite having a few members blown away by EB.
• Objects providing cover to enemies (bonus AC makes them harder to hit)
• Breaking line-of-sight (casting EB becomes impossible)
• Ancillary goals which are poorly served by EB (like the need to take people alive, or a need to interact with the environment which uses the Warlock's actions on other things)
• Opportunity costs. Your Warlock might be especially good at Eldritch Blast-ing, but they may also have spells, class features, or other options which are valuable (or crucial) to success. Setting up situations where there is a problem only a non-EB action from the Warlock can solve may make blasting less attractive (at times)
• Enemies/environmental hazards which impede spellcasting (such as frequently trying to grapple/restrain the Warlock)
• Enemies which are specialized to deal high damage to the Warlock, representing enemies' high priority on taking the Warlock out of the fight (high-damage snipers, for example)

###Hard Counters:

Hard counters are strategies which specifically neutralize or negate EB. I have fewer examples of these because I use them so sparingly-- they take away the fruit of a major investment this player made over other options:

• An antimagic field is going to short-circuit the EB-spamming strategy. Plentiful spell slots/spell-like abilities used to cast Silence or Counterspell can also frustrate your Warlock (credit to Renegade in comments for Silence and Counterspell)
• Enemies modified to be especially resistant to EB style attacks (they might have unreasonable AC, intended to be defeated by spells with saves)
• Enemies naturally resistant or immune to EB, like Helmed Horrors (credit to RonLugge in comments)
• Lingering effects. There aren't a ton of options to do this (thankfully), but enemies might start using abilities that reduce the Warlock's CHA stat, temporarily or permanently. I've not done this to the Warlock, but attribute penalties make for interesting situations every time I've encountered them.

I have this exact issue in a game I'm running (and the warlock can now fly, making him even more effective!). My strategies are still evolving, but I broadly have two categories I use to provide challenges for him: hard counters and soft counters.

Of those, I strongly prefer the soft counters.

###Soft Counters:

Soft counters are anything which frustrates or complicates the effectiveness of Eldritch Blast. The spell still exists, and would work well against enemies if the player can get around the obstacles, or would be a good idea if not for side effects. Examples of this include:

• The most important soft counter: smart tactics! Groups of enemies coordinating towards a common goal might succeed despite having a few members blown away by EB.
• Objects providing cover to enemies (bonus AC makes them harder to hit)
• Breaking line-of-sight (casting EB becomes impossible)
• Ancillary goals which are poorly served by EB (like the need to take people alive, or to preserve clothing or items while a solid EB hit might destroy them, or a need to interact with the environment which uses the Warlock's actions on other things)
• Opportunity costs. Your Warlock might be especially good at Eldritch Blast-ing, but they may also have spells, class features, or other options which are valuable (or crucial) to success. Setting up situations where there is a problem only a non-EB action from the Warlock can solve may make blasting less attractive (at times)
• Enemies/environmental hazards which impede spellcasting (such as frequently trying to grapple/restrain the Warlock)
• Enemies which are specialized to deal high damage to the Warlock, representing enemies' high priority on taking the Warlock out of the fight (high-damage snipers, for example)

###Hard Counters:

Hard counters are strategies which specifically neutralize or negate EB. I have fewer examples of these because I use them so sparingly-- they take away the fruit of a major investment this player made over other options:

• An antimagic field is going to short-circuit the EB-spamming strategy
• Enemies modified to be especially resistant to EB style attacks (they might have unreasonable AC, intended to be defeated by spells with saves)
• Lingering effects. There aren't a ton of options to do this (thankfully), but enemies might start using abilities that reduce the Warlock's CHA stat, temporarily or permanently. I've not done this to the Warlock, but attribute penalties make for interesting situations every time I've encountered them.

I have this exact issue in a game I'm running (and the warlock can now fly, making him even more effective!). My strategies are still evolving, but I broadly have two categories I use to provide challenges for him: hard counters and soft counters.

Of those, I strongly prefer the soft counters.

###Soft Counters:

Soft counters are anything which frustrates or complicates the effectiveness of Eldritch Blast. The spell still exists, and would work well against enemies if the player can get around the obstacles, or would be a good idea if not for side effects. Examples of this include:

• The most important soft counter: smart tactics! Groups of enemies coordinating towards a common goal might succeed despite having a few members blown away by EB.
• Objects providing cover to enemies (bonus AC makes them harder to hit)
• Breaking line-of-sight (casting EB becomes impossible)
• Ancillary goals which are poorly served by EB (like the need to take people alive, or to preserve clothing or items while a solid EB hit might destroy them, or a need to interact with the environment which uses the Warlock's actions on other things)
• Opportunity costs. Your Warlock might be especially good at Eldritch Blast-ing, but they may also have spells, class features, or other options which are valuable (or crucial) to success. Setting up situations where there is a problem only a non-EB action from the Warlock can solve may make blasting less attractive (at times)
• Enemies/environmental hazards which impede spellcasting (such as frequently trying to grapple/restrain the Warlock)
• Enemies which are specialized to deal high damage to the Warlock, representing enemies' high priority on taking the Warlock out of the fight (high-damage snipers, for example)

###Hard Counters:

Hard counters are strategies which specifically neutralize or negate EB. I have fewer examples of these because I use them so sparingly-- they take away the fruit of a major investment this player made over other options:

• An antimagic field is going to short-circuit the EB-spamming strategy. Plentiful spell slots/spell-like abilities used to cast Silence or Counterspell can also frustrate your Warlock (credit to Renegade in comments for Silence and Counterspell)
• Enemies modified to be especially resistant to EB style attacks (they might have unreasonable AC, intended to be defeated by spells with saves)
• Enemies naturally resistant or immune to EB, like Helmed Horrors (credit to RonLugge in comments)
• Lingering effects. There aren't a ton of options to do this (thankfully), but enemies might start using abilities that reduce the Warlock's CHA stat, temporarily or permanently. I've not done this to the Warlock, but attribute penalties make for interesting situations every time I've encountered them.