Running a Summoner in the Planescape setting

[King of Vrock]

I'm running a high level mythic Planescape game using Pathfinder rules. For the most part I'm ignoring mechanics from 2e such as enhancement bonuses changing from plane to plane other than a sword of the planes.

I have a Summoner (naturalist) in my group and I don't want to completely nerf his eidolon, but I want to keep Sigil acting as the Cage. So far my workaround is he would have to perform his summoning ritual near an active portal to the plane that matches his alignment, namely the Beastlands. The portal key would act as a spell focus or focus component. However what to do when he needs to dismiss his eidolon or more important if it gets killed in battle. One thought would be he'd need to find a portal and open it within a minute (same as casting time of his ritual) for his eidolon's essence to escape. He's got ways to keep his eidolon from being banished, an eidolon anchoring harness mainly. But I feel at some point during an intense boss fight it should be threatened with death (as an outsider it would need limited wish, wish, miracle, or true resurrection to be brought back).

As we're playing a mythic game I'm thinking of giving him a campaign trait that gives a bonus to the analyze portal or warp sense spell's caster level check to identify a portal's secrets and allows him to substitute a Use Magic Device to trick the portal into thinking he has the correct key (like an unchained skill unlock).

Any other alternate ideas?

[Lady Asharah]

I would imagine the larger question should be, how do you handle Summon spells?

Because an Eidolon would follow the same rules. If wizards can summon monsters in combat, a Summoner would be able to call their Eidolon without issue. If wizards *can't* summon monsters in combat, then I think you have a few bigger problems to work out aside from an eidolon.

[Bjørn Røyrvik]

I could see my way to allowing the eidolon to be be locked in a personal demiplane located within the caster himself, but I would still enforce the ban on other summons into/out of the Cage.

I would not allow anyone to 'trick' portals. They are under the direct control of the Lady and allowing anyone to mess with that is undermining a key aspect of Sigil and Her power.