I've hit Google, Reddit and the forums with this but I'll be honest and say even with the debates and FAQ I don't fully understand what's actually considered an ability based check.
Concerning planar travel and strongly aligned planes.
Rules:
Strongly Aligned: On planes that are strongly aligned, a –2 circumstance penalty applies on all Intelligence-, Wisdom-, and Charisma-based checks made by all creatures not of the plane's alignment. The penalties for the moral and ethical components of the alignment trait stack.
So what will this actually make a difference to?
Base ability checks - YesSkills using Int/Wis/Cha?
Spell caster checks using on Int/Wis/Cha?
Will saves?
I've seen the argument for "d20 + ability + other" is an ability based check but "d20 + other + ability" isn't an ability based check.
However under those conditions doesn't the penalty of being on another plane strongly opposing your alignment become a little weak? There are not a great number of "d20 + ability + other" checks in the game.
Only FAQ information I could find close to this. Which leads me to think all skills using an ability are an ability based check?
Alternate Ability Score-Based Checks: If I change the key ability score of a skill (or other check), for example, if I change Knowledge from Intelligence to Charisma, is it no-longer an Intelligence-based check? Is it now a Charisma-based check?
Generally yes—at the time of rolling a check, if you substitute the ability score, the check is now based on the new ability score. In the example, at the time of rolling, Knowledge would now be a Charisma-based skill and not an Intelligence-based skill for you, which would affect things like feats, spells, or items that grant bonuses on checks based on their key ability score (like circlet of persuasion). However, if you are adding a second ability modifier to a check, this is not the case. For instance, when adding both Wisdom and Dexterity on initiative checks, initiative is still a Dexterity check, not a Wisdom check. Also, this changes the check only at the time of rolling, so this does not change static class features or options made during character building such as your class’s class skills. Classes that receive “all Intelligence-based skills” as class skills, for instance, are the victim of sloppy writing, and furthermore sometimes effects might muddy the water by only changing the ability dependency sometimes and not others, which is why you check the new dependency only for a specific given roll.
Appreciate the help and clarification to come.
an ability based Check would be anytime when the format is roll a d20+ability+other, as the default.
So,
base ability checks: Yes
Skill checks: Yes
Caster Checks: No
Concentration Checks: Yes
Saving Throws: Maybe
Caster checks are d20 plus caster level. Outside of a couple of feats and items you don't tend to get much in the way other other bonuses to caster checks. These are different from concentration checks which always include the casting stat of the character making the check.
A will save could probably be considered a "wisdom based check". But I couldn't find anything that stated this one way or another.