Early drafts of the set felt like they were lacking focus as the mechanics were spread too thin. As a result, I've decided to lay down the following guiding principles for where the mechanics should appear.
Siphon - All colours, but green/white creatures must not be druids
Discharge (
) - UR (Wizards) Primary, WB secondary, none in G
Infuse (
) - WG (Druids) Primary, UB secondary, none in R
Vanguard (
) - RB (Warriors) Primary, WG secondary, none in U
Survivor (
) - UG (scouts) Primary, BR secondary but no clerics with survivor
Lineage (
) - WB (clerics) Primary, all colours secondary
Cycling (
) - WBR subtheme, UG permitted (especially for cycles)
If you come across a card which goes against this roadmap, flag it in a comment!