Tibia

Before I start, here are a few definitions of terms that I will use throughout the concept:

Aggressive Actions: Any action that has a negative influence on any creature, those include:
All attacks (direct and indirect, single field and area based) - e.g. fields, bombs, UEs, missiles etc.
All debuffs and anti-buffs (direct and indirect, single field and area based) - e.g. paralyze, cancel invis etc.
Everything that hinders the movement of other creatures - e.g. fields, walls, blocking with characters and summons etc.
Everything that destroys things - e.g. destroy field, desintegrate

Supporting Actions: Any action that has a positive influence on any creature, those include:
All healing (direct and indirect, single field and area based)
All buffs and anti-debuffs (direct and indirect, single field and area based) - e.g. party buffs
Using items on others with positive effects - e.g. potions

PvP-activation: The clearly defined declaration of a player against another character to have the intention to perform aggressive actions against him
Aggressor: A character and his summons, who performs a PvP-activation and is not a "protector" (see below) against his target
Defender: A character and his summons, against whom a PvP-activation is performed by a character who is not a "protector" (see below) against him
Group: Parties and guilds
Protector: Member of the same group of a defender
Basic rules for influencing other characters outside of any PvP-situation:
Aggressive actions cannot be performed directly against other characters and their summons and they will also not have any indirect influence on them as long as there is no PvP-activation running between the involved characters
Obstacles can simply be ignored, so walls, fields etc simply have no effect on other characters
Characters can swap generally without further checks with other characters and their summons

Supportive actions can be performed directly on other characters and their summons and will also have all indirect influence that is usually expected on them as long as there is no PvP-activation running between the involved characters

Performing a PvP-activation:

Ways to activate PvP
Select the wanted target in the battle list or in the game window (exactly what you have to do now to directly attack)
Optionally, you can rightclick on a character in battle list or game window who is currently an aggressor and in your group and select "join aggression"; this will perform PvP-activations against all his defenders

Protection against unwanted PvP-activations (safe hand and battle list filters in the Flash-Client)
1) All aggression possible: you can get any PvP-mark, PZ-block and produce unjustified kills
2) Only aggression against skulled characters: you can get at max a private PvP-mark and a PZ-block
3) Only protection: you can get at max a private PvP-mark
4) Only defender: you cannot get any negative consequences

Basic rules for groups (many of these only apply to parties, but we'll stick with the "group" term anyways):

Members of the same group cannot perform one-sided PvP-activations within the group
You can only leave a group when you have no logout block (battle sign)
Optional: After leaving a group you get a short delay on PvP-activations
The group leader can generally not invite anyone who is currently in a PvP-situation
If there is at least one PvP-activation against a member of the group, the leader cannot perform further invitations
If there is at least one PvP-activation against a member of the group, all members also retrospectively become potential protectors (for party when someone who already was invited joins, for guilds when a member logs in after the PvP-activation)

Entry conditions into a PvP-situation:

One-sided PvP-activation:
Characters can activate PvP anytime, unless they are standing in a stack of creatures not on top, they are in a protection zone or they have no vocation (are Rookgaard characters)
The PvP-activation can be performed against anyone, except against members of the same group, against characters in a protection zone or against characters without PvP-mark when one has a black skull oneself
PvP-activations generally have to be performed against single characters
To support an aggressor of your own group, you can use the option "join aggression" to activate PvP against all his defenders

PvP-activation with mutual agreement, will be called duel (details to this are still not defined, but we will need something like this):
It is possible to activate single or group duels
Activating a duel always implies that both sides get a private PvP-mark and there may not be any protectors for either of them
There may also be special conditions set
Duels can also be performed within the same group (so training is possible)

Basic rules for influencing other characters within a PvP-situation:

An aggressor gets a logout block and a PZ-block and is judged by the Skull system instantly upon the PvP-activation
There may be a short delay after the PvP-activation before the aggressor can actually start performing aggressive actions against his target
A defender gets a logout block instantly upon receiving the PvP-activation
A defender can instantly perform aggressive actions against his aggressor and will not get any PvP-mark or a PZ-block for it
If a character is in a group:
PvP-activation against a character in a group implies that the aggressor also gets a PvP-mark visible for all protectors
Protectors can individually then activate PvP against that aggressor, they then get a logout block, no PZ-block and a PvP-mark visible only to the aggressor
Protectors can instantly after their activation perform aggressive actions against the aggressor
PvP-activation by a character in a group has no implications on the other members of the group

When characters get involved in a PvP-situation, the basic rules for influencing other characters change as follows:
Aggressive actions against characters that are involved in the same PvP-situation as oneself are now enabled, not against characters involved in other PvP-situations
New field based obstacles (fields, walls, bombs etc) only work if they were created after the PvP-activation
Swapping is not possible

Supporting actions on characters that are involved in any PvP-situation are not possible anymore, except:
on members of your own group that are not aggressors, you get no penalty for supporting them
on members of your own group that are aggressors, then only after you select "join aggression" and only as long as that aggressor does not add another PvP-activation after you joined

Exit conditions from a PvP-situation:

PvP will automatically be deactivated as follows:
For all involved of one PvP-activation when
the aggressor looses his battle sign
the aggressor dies

For an individual defender or protector when
he looses his battle sign
he dies

General new displays:
At a character whether he is in a party and how many members and inviteds that party has
At a character whether he is in a guild and how many members it has and how many are online
At a summon that it is not a wild creature

Skull System
We will keep the orange, white, red and black skulls as they are now
The yellow skull will be replaced by the additional PvP-Flagging

Additional PvP-Flagging
We would use the frames around characters / fields as display
A yellow frame will mark:
Characters and their summons who are in a PvP-situation with oneself
Fields on which there are magic fields / walls etc. that were created by one of the above characters after the respective PvP-activation
Fields on which there are magic fields / walls etc. that were created by oneself or wild creatures
Ones own character if the character is still in at least one active PvP-situation

An orange frame will mark:
Characters that are aggressors against at least one member of ones own group and which do not have a yellow frame

A brown frame will mark:
Characters that are in at least one PvP-scenario, but do not have a yellow or orange frame

Generally, all skulls and frames begin to blink 5 seconds before they disappear and are thus prolongable by another attack during the blinking period

Differences for other PvP server types:

Optional PvP
One-sided PvP-activation is not possible
Swapping here is Ghosting
There is no Skull System
All kills are justified

Hardcore PvP
No PvP-activations are necessary because everyone is always already within PvP-scenarios, that means that all basic rules always apply as within a PvP-situation (so no swapping, everything influences everyone always etc.)
There is no Skull System
All kills are justified

Unfortunately, I do not have time left to post more than just this concept. I will be away for the whole next week. I will read your discussion about it, very unlikely I will post a few things. I am very interested in your feedback and thoughts on this.

Also consider all positive and negative side effects of this.

The following concept is a more generalized proposal for a PvP-system that does in our opinion address almost all issues regularly raised and provides a sound basis for an extended war system too. The proposal is for now only formulated without direct consideration for the war system, so it does not include the Focus Group War System proposal, but it does not exclude it either, and it has quite a few implications that already pave the way for that system too.

The system is based and designed to fit Open PvP servers. We would also apply the same system to the other server types, but with a few central differences in rules. Those differences are listed at the end of the proposal.

So, here we go:

Goals:

PvP must still be possible anywhere, anytime and against anyone (with a very few defined exceptions)
Taking influence on PvP situations must always be assessable by the system, including all indirect influence taken
Accidental actions that have a bearing on PvP and side effects for those performing them should not be possible
Parties and guilds as cooperative constructs should play a specially designed role in PvP