When it comes to summoning, there’s a lot of things that are risky for the game balance. For most of those there’s already balancing mechanisms in place, such as with the Astral Spirit Index, but there’s a few cases that are a bit problematic.
The two cases treated here are the duration of Bound Spirit Services, and dealing with Oversummoners. The first doesn’t often come up but the second I have frequently seen debates about. Debates I participated in to get the math right. The math is skippable though.
A third houserule I designed is dealing with Free Spirits, but that’s not really a rule I suspect people have a need for. Anyway, if someone has any other problems with conjuring and want some houserule input, just contact me over at Shadowrun Universe by private message. =)
Rule: Bound Spirit Services last until dusk/dawn
Since a Bound Spirit does not expire at Sunset/Sunrise, it’s possible to make them sustain specific powers/spells indefinitely. Now this comes with consequences. However since Sustaining does not require LOS and Critter Powers normally (unless GM-called otherwise) are immune to Barriers, these consequences can be easily avoided. So it’s far too easy for a mage to have a single Spirit permanently sustain Movement and Concealment on them, and possibly even Endowment.
Another problem is that buff-spells from a Spirit of Man can also become rather permanent this way, with having to blow up or slip past Mana Barriers as only concern. While having a Spirit sustain your own spell is only its Force in Combat Turns, Innate Spell would avoid that and be indefinite.
The easiest solution to this is limiting how long services last. When a service does not explicitly state a deadline, it will now not last past dusk/dawn, preventing someone from walking around with permanent buffs for 1 service per buff. You still get all the other benefits from Bound Spirits, but cannot use them as cheap buffslaves. This way the GM won’t have to dig into the other consequences, which take time, and can simply block the sneaky trick from the get-go.
Rule: Oversummoned Spirits resist with Edge
Let’s start with an important disclaimer: Some may say this is not allowed by the rules, so the GM cheats. They are wrong. p304 says that summoned and bound Spirits cannot use their own Edge pool. However, a Spirit you are Summoning is not yet summoned until you succeed, so is allowed to use Edge against the Summoning attempt itself.
There will be a time where a player decides to go down the line and use all they got to summon a Force 12 Spirit. They may score only 1 or 2 services, but the Spirit will be completely invincible. At Hardened Armor 24 they are practically immune to every kind of non-magical attack, against Indirect Spells they have a massive defense pool, against Area effects they got plenty of Initiative to burn, and they laugh in the face of any spell they resist with their Attributes. Even Direct spells are harmless, especially if it’s a Spirit with Magical Guard.
In other words, such Spirits are a game-changer. Just like how gangers stand no chance against a Force 6, even a huge PR6 enemy team will be butchered by a Force 12. If used for the climactic boss-fight where everything is on the line, such a high-risk move makes sense. The problem arises when it is NOT a high-risk move and used as a frequent weapon instead.
Just like how wards are limited in how much they balance out Quickening, so is drain in itself limited in how they balance out Summoning. Now a anti-Summoning dice pool of 12, with hits doubled in drain, may seem like it is a decent risk. But at the same time it’s the same dicepool that is used against Binding, and people still have Force 6 Spirits. Sure, they got a safer environment but it still boils down to the same success chances and drain risks.
WARNING: The next section contains a lot of math. Skip to “Math Done” to get to the abbreviated version.
Let’s take a look at a slightly-buffed Shaman. At 5 Willpower, 8 Charisma and +4 drain dice from whatever origin, they’ll be at 17 drain dice. Let’s assume they’re also at 17 Summoning dice, which once again is quite doable.
First, the Summoning itself: There’s 2/3 chance to succeed, and half the successful summons will be at 3+ services. Plenty to butcher your way through whatever your GM throws at you.
Second, the Drain: 2/3 chance to take Drain, 1/3 chance to score 4+ drain, and assuming 10 Physical Monitor 1/31 odds at going unconscious (which means disaster). Those are rather excellent odds, since with combined numbers you have roughly 1/3 odds to fail generally. (More exact numbers would require a handwritten program to analyze the odds, but that 1/31 and a bit less than 1/3 odds mostly overlap so it still is ~1/3 overall.)
If we bring Second Chance into the Summoning, failure is at ~1/32 and average services are past 5. And drainwise we’re suddenly at only 30% chance to get hit by ANY drain. 10+ odds are at ~1/3.000, 6+ at ~1/25 and 3+ at ~1/6. Let me repeat that: At the expense of 2 Edge, a player can score 5 services and take only 1P in drain from an unbeatable Force 12 Spirit. So all they have to do is make sure they have 3+ Edge, summon this at the start of a run and make it tear down the enemies without having to sweat at all.
It gets worse. Let’s assume the Shaman has +4 Charisma, +4 Willpower, 2 Initiations and a Force 3 Centering Focus. That’s 26 drain dice, which means that unedged their odds are worse but they still are at ~1/5 for 3+ drain, ~1/30 for 6+ and only ~1/150 to get hit with 10+. And even IF this worst scenario hits, they can still Second Chance it.
So unfortunately, Drain is not enough of a deterrent by itself against Oversummoning. Which means that Oversummoning is a high threat to the game balance and any player who so desires can greatly upset the game and ruin the fun for all. Now normally the social contract applies, but what if you cannot depend on that?
That’s where we grab back to SR4 Street Magic. In there was a rule, not an optional rule but a simple core rule, where Oversummoned Spirits always resisted with Edge. Back then their Edge equaled their Force so they resisted with Forcex2 exploding dice. Needless to say a Force 12 Spirit would utterly butcher you in drain.
In SR5 the Edge has become less, it is now half their Force. Which means an Oversummoned Force 8 Spirit could either have 8 rerolled dice (averaging 4.44 hit) or 12 exploding dice (averaging 4.8 hits). In other words, a Force 8 Spirit using Edge would be better off than that Force 12 Spirit we used in the previous scenarios.
Let’s take a look at 12 exploding dice. Against a Force 12 spirit our 17 second-chanced dice meant massive drain reduction, with only 1/6 chance to get hit with 3+ drain and zero odds at actually dying. With Edge-use the Force 8 Spirit is already at 30% and 1/140 death chances for an unwounded Body 3 Mage. So the Force 8 Spirit is significantly tougher than the Force 12 was.
Meanwhile, 26 rerolled drain dice versus the Force 12 Spirit would become ~1/3 at 3+, ~1/6 at 6+, ~1/16 at unconscious for Body 3~4, and ~1/80 death chances for a Body 4 mage. Definitely odds you do NOT want to frequently take, no matter how good you are.
Disclaimer: Said math was done with an emulation of an exploding die which cannot explode more than 4x, so only 5 hits per die are possible. However, this manages to emulate an exploding dice to near-reality at the point where the full numbers would differ only past the decimal cut-off.
In short, Drain is unfortunately far from enough of a balance factor against an eager Oversummoner, and even maximum-Force Spirits are perfectly doable for someone who tries, which greatly upsets the game balance.
By making Spirits employ Edge against the Oversummoning, this is balanced out better and said mechanism will not harm normal Conjurers in any way. And when a player can make a good argument that in a specific situation the Spirits may be willing to help, the GM can always waive the Edge use for that one situation where it comes down to the line.