Where would you put this homebrew's CR?

[Tawmis]

Essentially a Drider (lower AC, lesser HP) - but has the body of a Phaser Spider, which allows it to do what a Phaser Spider does.

The entirety of this homebrew can be seen in this image - would love feedback.

https://i.ibb.co/k89r13m/Image6.png

[J-H]

Using Blog Of Holding card for reference:

AC 16 CR 9
HP 95, no special DR CR 5
Attack +6 CR 5
Damage 2d8+3 x 3 = 36/rd CR 6
Specials: Minor spells, no change; Spider climb makes it a bit harder to engage in melee, favoring archery. Ethereal jaunt gives it good mobility and the ability to get away.

CR 6 as listed looks about right to me. I'd bump the Dex up to 18, because +6 to hit is going to be a lot of misses against a party with some front-liners.

[quindraco]

I put this through the standard CR calculator, but something the DMG has never had useful guidance on is accurately calculating the damage output of this thing's bite. In this case, if I assume the save is failed but calculate CR strictly on the to-hit value of the bite, as the DMG mysteriously recommends, I get OCR 7 (45 damage from bite-sword-sword), which combined with its DCR of 2 gets a net CR of 5. But that's ludicrous.

If I assume the save against the bite succeeds, the melee combo is 36 damage, so OCR 5, and net CR 3. Far more reasonable.

But neither of those makes any god-damn sense, because the thing's INT and WIS are far too high for it to be stupid enough to engage the party in melee. Assuming its ethereal jaunt ability lets it stay in the Border Ethereal, what it should normally do is bonus action into the Prime Material in ambush position and fire, next turn probably fire and then bonus action ethereal to move into position while invisible and indestructible.

If I calculate the longbow's DPR I get OCR 5, and if I treat the creature as flight-capable while also range-capable, I get DCR 3, for net CR 4. That sounds like the most reasonable conclusion.

That's with the sheet as written - you have some incorrect values. The longsword should be at +5 to hit, not +6. I didn't remath the melee OCR with a +5 to hit longsword, but if you correct the bonus, that only reinforces the fact that it should primarily be a ranged attacker.

So my final answer is CR 4, although there's a case to be made for CR 5 or CR 3. The CR 6 on the sheet is right out.

This particular creature will have a higher than normal CR if you field it in a group, though - much like pack tactics being better with 2 or more kobolds, the ethereal jaunt trick is more than twice as good with a second phaspider, as they can guarantee things like a pincer attack - a party has no credible way of keeping a second phaspider away from their backline.

EDIT: Math above is with the hit dice and Con score you listed, 10d10 hit dice and Con 17, which is 85 hit points, not 95. Giving it 11d10 hit dice raises its hp to 93, which is the same DCR as 95 - to whit, DCR 4 (due to the DCR from its HP going up from 1 to 2), which changes its net CR from 4 to 4.5, which means its net CR rounds to 5. So CR 4 with 85 hit points, CR 5 with 93 (or 95) hit points.

[Tawmis]

Thank you both! And good catch - originally I had the HP lower, so I had it at 10. But I wanted a creature with a good fight - so I raised it to 95 hp, forgot to change the HD.



So my final answer is CR 4, although there's a case to be made for CR 5 or CR 3. The CR 6 on the sheet is right out.


The only reason I'd put it higher than CR 3, for sure - is a Phase Spider is a CR 3 (just by itself). So I figure, Phase Spider with more HP and spell casting, should rank higher.
A Drider is CR 6 (but as I said, this has a lot of similarities with Driders) - but has lower AC and lower HP (significantl, 30+ HP difference).
So I was coasting between 5 or 6.

[J-H]

Another way to eyeball this is a comparison against other CR 5-6 monsters. I didn't immediately see anything ranged on the basic MM list. I picked 4 and eyeballed it.

CR 5 Air Elemental:
HP 90 close match
AC 15 close match
Mobility close match (flight) but AE can phase out to retreat more easily
DPR 2d8+5 (14) x 2 per = 28/rd at +8 to hit. Air Elemental's damage is a bit lower but to-hit is higher.
Overall about even.

CR 5 Drow Elite Warrior
HP 78 a bit lower
AC 18 a couple of points higher, plus parry
Mobility Phasider wins
DPR 4d6+4 (18) x 2 = 36/rd in melee at +7 to hit. Near exact match.
A Phasider is going to wipe the floor with a Drow Elite Warrior due to mobility and range and clearly outclasses it as a threat.

CR 5 Revenant
HP 136 substantially higher, plus regeneration
AC 13 substantially lower, balances the HP
Immunities: Has some
Mobility nothing special, Phasider wins
DPR 2d6+4 (11) x 2 = 28/rd in melee at +7 to hit. Slightly lower.
The revenant is even more outclassed than the Drow Elite Warrior in most circumstances.

CR 5 Troll
HP 84 Phasider slightly higher, but troll regenerates
AC 15 Troll slightly lower
Mobility: Phasider's ahead
DPR 5d6+12 total across 3 attacks = 29.5/rd in melee at +7 to hit.
The phase spider drider does more damage, has a higher AC, and more mobility than the troll.

I'm going to stick with CR 6 being about the right spot. CR 3-4 is substantially too low.