Dark Souls 2 Soul Memory Calculator / Visualiser
This is mirrored with my Steam Guide.
In general, you can't connect between NG and NG+ at all. However, NG+, NG++, and so on can connect to each other. Since the SotFS patch, there are no restrictions based on playthrough.
- You can only see White Sign Soapstone summon signs when human and there is still a boss alive in the area you are in. Small White Sign Soapstone summon signs will show up even after the boss is dead.
- Being in the Heirs of the Sun Covenant doesn't increase the SM range, it simply makes your phantom/shade and sign appear golden. Whether it increases the chance of your sign appearing is unconfirmed.
- The Name-Engraved Ring only seems to expand the SM range for co-op summons, but the filtering effect works with the Red Sign Soapstone and Dragon Eye too.
- You can't summon or invade in Grave of Saints and Doors of Pharros, these areas are exclusively for Rat King Covenant PvP.
- You can only summon one phantom or shade in Belfry Luna and Belfry Sol, presumably to prevent you ganking with 3v2 fights.
- The Blue Sentinels arena has no restriction on Soul Memory.
- Whether the Brotherhood of Blood arena has restrictions is currently unknown.
- Abyss invasions are unconfirmed, but you can assume they work the same as regular Cracked Red Eye Orbs for now.
- Mirror Squire invasions (coming out of the Looking Glass Knight's shield in NG+ and above) seem to ignore the NG/NG+ divide, although this is unconfirmed. Otherwise you can assume they work the same as the regular Red Sign Soapstone.
- Ranges for the Guardian's Seal and Crest of the Rat haven't been retested for the latest patch yet. The new range is likely slightly larger than what is currently listed.