|As 5th edition rules state, Mind Scan can be used to "count minds". However, I will use these house rules instead of the rules in the book.|
When using Mind Scan for this purpose, Mind Scan is an "active" sense in that the use of it can be picked up by anyone in the target area with Mental Awareness. The character doing the mind scan declares the target radius and desired effect. Mind scans emanate from the mentalist though the mentalist can declare a less than 360 degree radius if he only wants to search in a specific direction. Possible scans are 60 degrees, 120 degrees, 180 degrees, 240 degrees and 360 degrees.
There are three possible effects: Accurate Count of Minds, Accurate Count and General Location of Minds, and Accurate Count and Exact Location of Minds.
Accurate Count of Minds
The mentalist gets an accurate count of all minds in the target area for which the effect roll exceeds the target's EGO + Mental Defense.
Accurate Count and General Location of Minds
The mentalist gets an accurate count, and a general location (within 10% of distance) of all minds in the target area for which the effect roll exceeds the target's EGO + Mental Defense + 10. The GM should feel free to generalize if the mentalist is searching a huge area. General Location (within 10% of distance) means that if the mentalist picks up a target that is, say 100 meters away, they can pinpoint their location within 10 meters (10% of 100 meters). If the target was 250 meters away, they could pinpoint their location within 25 meters (10% of 250 meters).
Accurate Count and Exact Location of Minds
The mentalist gets an accurate count, and an exact location (suitable for targeting attacks), of all minds in the target area for which the effect roll exceeds the target's EGO + Mental Defense + 20.
Agent 1: EGO 14, MD 0, 80"
Agent 2: EGO 10, MD 0, 90"
Agent 3: EGO 18, MD 7, 50"
Agent 4: EGO 23, MD 10, 40"
Agent 5: EGO 29, MD 19, 20"
1) A zho mentalist suspects that there are some enemy agents in the section of woods that he and his 10 men are searching. He declares that he will do a mind scan out to a 300 meter (150") radius. He rolls his 8d6 and gets a 21. He gets an accurate count of all minds for which the result roll of 21 exceeds the target's EGO + Mental Defense. There are five enemy agents in the area (see above) of which three of them have an EGO + Mental Defense of 21 or higher (agents 3, 4, & 5). None of the 10 zho soldiers have an EGO + Mental Defense higher than 21 so the zho mentalist ends up with a final count of 12 (excluding himself). Thus he knows that there are two minds (agents 1 & 2) that are unaccounted for and can be presumed to be enemy agents. He has no way of knowing about the three other agents who avoided detection.
2) Now that the zho mentalist knows there are enemies, he decides to narrow his scan. He has all of his men stand behind him and does a second scan with an arc of 240 degrees that will not catch his men. Again he rolls the effect and this time gets a 26. All of the enemy agents are in his scanning arc of 240 degrees and within his declared range of 150". Three of the enemy agents have an EGO + Mental Defense of 26 or less (agents 1, 2, & 3) and so the zho gets an accurate count of three minds.
3) The zho performs the exact same scan as before but this time declares that he wants accurate count and general location. He rolls a 25 for effect. To get general location, he needs to exceed the target's EGO + Mental Defense + 10. He gets an accurate count of 2 (agents 1 & 2) and the general location of both within 10% of distance. Thus he learns that agent 1 is between 72 and 88 inches away and agent 2 is between 81 and 99 inches away. Now that he knows the general location, he can attempt another scan to try to get exact location but needs to exceed the target's EGO + Mental Defense + 20, so he will have to make an effect roll of 31 or higher to get even the weakest minded agent (agent 2).