diff --git a/d2char.c b/d2char.c
index 5e90cb6..174aedf 100644
--- a/d2char.c
+++ b/d2char.c
@@ -136,6 +136,10 @@ size_t getLastPlayed(D2CharHeader* c, char* buf, size_t bufLen) {
 }
 
 const char* getSkillName(int skillID) {
+    if(skillID > D2S_SKILL_NUMSKILLS) {
+        fprintf(stderr,"libd2char error: skillID %d doesn't exist\n",skillID);
+        return NULL;
+    }
     return skills[skillID];
 }
 
diff --git a/d2char.h b/d2char.h
index 785d0a3..562345b 100644
--- a/d2char.h
+++ b/d2char.h
@@ -17,7 +17,7 @@
 #define D2S_HOTKEYS_LENGTH 64
 #define D2S_CHAR_APPEARANCE_LENGTH 32
 #define D2S_DIFFICULTY_LENGTH 3
-#define D2S_WAYPOINTS_LENGTH 81
+#define D2S_WAYPOINTS_LENGTH 80
 #define D2S_NPCDATA_LENGTH 51
 
 #define D2S_CHARSTATUS_HARDCORE 0x04
@@ -92,11 +92,18 @@ typedef struct __attribute__((packed)){
     uint8_t unknown6[144]; // TODO
     D2QuestData questData;
     uint8_t waypointData[D2S_WAYPOINTS_LENGTH];
+    uint8_t unknown7; // TODO. Apparently this is always 0x01
     uint8_t NPCIntroductions[D2S_NPCDATA_LENGTH]; // TODO: Not implemented
 } D2CharHeader;
 
 // TODO: All setX functions
 
+// TODO: Load from file.
+// int loadD2CharFromFile(const char* file, D2CharHeader** header, void** data);
+
+// TODO: Write to file.
+// int writeD2CharToFile(const char* file, D2CharHeader* header, void* charData,)
+
 uint32_t calcChecksum(D2CharHeader* c, void* charData);
 int checkChecksum(D2CharHeader* c, void* charData);
 int isHardcore(D2CharHeader* c);
diff --git a/d2mercs.c b/d2mercs.c
index a1af155..79b019f 100644
--- a/d2mercs.c
+++ b/d2mercs.c
@@ -1,5 +1,7 @@
 #include "d2mercs.h"
 
+#include <stdlib.h>
+
 int _getMercType(int mercID) {
     if(mercID >= 0 && mercID <= 5) {
         return D2S_MERCTYPE_ROGUE;
@@ -16,5 +18,8 @@ int _getMercType(int mercID) {
 
 const char* _getMercName(int mercID, int mercNameID) {
     int offset = _getMercType(mercID);
+    if(offset == D2S_MERCTYPE_UNKNOWN) {
+        return NULL;
+    }
     return mercNames[mercNameID + offset];
 }
\ No newline at end of file
diff --git a/d2mercs.h b/d2mercs.h
index 218eaec..bf0cb67 100644
--- a/d2mercs.h
+++ b/d2mercs.h
@@ -3,6 +3,8 @@
 
 #include "d2strings.h"
 
+// TODO: return compound data (type, subtype, difficulty, not just a string)
+
 // The values here are the offsets of each merc's names in the table.
 // i.e: Merc names from pos 41 to 61 are Desert mercs
 //
diff --git a/d2quest.c b/d2quest.c
index 0758132..058529a 100644
--- a/d2quest.c
+++ b/d2quest.c
@@ -1,7 +1,13 @@
 #include "d2char.h"
 #include "d2quest.h"
 
+#include <stdio.h>
+
 void getCheckpointDescriptions(unsigned int quest, const char* *descriptions[16]) {
+    if(quest > D2S_QUESTDATA_NUMQUESTS) {
+        fprintf(stderr,"libd2char error: quest %d doesn't exist\n",quest);
+        return;
+    }
     memcpy(descriptions,(&checkpointDescriptions) + (quest * 16 * sizeof(const char*)), 16 * sizeof(const char*));
 }
 
@@ -17,7 +23,8 @@ uint16_t getQuestStatus(D2QuestData* d, unsigned int quest, unsigned int difficu
     } else if(quest >= D2S_QUEST_SIEGE_ON_HARROGATH && quest <= D2S_QUEST_EVE_OF_DESTRUCTION) {
         return d->quests[difficulty].expansionAct.questCheckpoints[quest - D2S_QUEST_SIEGE_ON_HARROGATH];
     }
-    return D2S_QUEST_UNKNOWN;
+    fprintf(stderr,"libd2char error: quest %d doesn't exist\n",quest);
+    return 0;
 }
 
 void setQuestStatus(D2QuestData* d, unsigned int quest, unsigned int difficulty, uint16_t questData) {
@@ -31,6 +38,8 @@ void setQuestStatus(D2QuestData* d, unsigned int quest, unsigned int difficulty,
         d->quests[difficulty].actData[D2S_ACT4].questCheckpoints[quest - D2S_QUEST_FALLEN_ANGEL] = questData;
     } else if(quest >= D2S_QUEST_SIEGE_ON_HARROGATH && quest <= D2S_QUEST_EVE_OF_DESTRUCTION) {
         d->quests[difficulty].expansionAct.questCheckpoints[quest - D2S_QUEST_SIEGE_ON_HARROGATH] = questData;
+    } else {
+        fprintf(stderr,"libd2char error: quest %d doesn't exist\n",quest);
     }
 }
 
@@ -98,6 +107,11 @@ int getSpecialQuestStatus(D2QuestData* d, unsigned int specialQuestState, unsign
 }
 
 void setSpecialQuestStatus(D2QuestData* d, unsigned int specialQuestState, unsigned int difficulty, int bool) {
+    if(difficulty != D2S_DIFFICULTY_NORMAL    || 
+       difficulty != D2S_DIFFICULTY_NIGHTMARE || 
+       difficulty != D2S_DIFFICULTY_HELL) {
+        fprintf(stderr,"libd2char error: difficulty %d doesn't exist\n",difficulty);
+    }
     switch(specialQuestState) {
         case D2S_SPECIALQUEST_AKARA_RESPEC:
             // This operation only makes sense if the quest is actually completed, otherwise ignore request
diff --git a/d2quest.h b/d2quest.h
index f9e049e..5e762bc 100644
--- a/d2quest.h
+++ b/d2quest.h
@@ -6,6 +6,7 @@
 #include "d2strings.h"
 
 #define D2S_QUESTDATA_HEADER_LENGTH 4
+#define D2S_QUESTDATA_NUMQUESTS 27
 
 enum D2S_QUEST {
     D2S_QUEST_UNKNOWN = -1,
@@ -500,17 +501,22 @@ typedef struct __attribute__((packed)) {
 typedef struct __attribute__((packed)) {
     D2ActData actData[4];
     D2XActData expansionAct;
+    // My guess is that the following `uint16_t`s all represents some quest data that was added after 
+    // the game was launched. This also explains why there's version data (supposedly) and length 
+    // of the quest data in bytes in the header.
     uint16_t akaraRespecData; // This uint16_t determines if the player has used Akara's respec or not
     uint16_t unknown1[6];
 } D2Quests;
 
 typedef struct __attribute__((packed)) {
-    const char* header[D2S_QUESTDATA_HEADER_LENGTH];
-    uint32_t unknown1;
+    const char* header[D2S_QUESTDATA_HEADER_LENGTH]; // Woo!
+    uint32_t unknown1; // This is likely version data
     uint16_t size; // in bytes
     D2Quests quests[3]; // 1 set for each difficulty
 } D2QuestData;
 
+// TODO: These functions are completely unsafe, and don't return success
+
 // Populates `descriptions` with static strings from library memory, no need to free.
 // `descriptions` contains one string for each bit field of the quest's uint16_t data.
 // Empty entries (non-existant or unknown checkpoints) will have NULL value. Be careful!
@@ -527,9 +533,10 @@ int isQuestCompleted(D2QuestData* d, unsigned int quest, unsigned int difficulty
 // Set bool to 1 to set the status or 0 to remove it
 void setQuestStarted(D2QuestData* d, unsigned int quest, unsigned int difficulty, int bool);
 void setQuestRewardCollected(D2QuestData* d, unsigned int quest, unsigned int difficulty, int bool);
+
 // When called to set the request to NOT completed (`bool` = 0), this will NOT set the reward collected status
 // which *may* render the quest unobtainable, this is done in case we may want to further modify the quest state.
-// If you want to mark the quest as not completed just to get the reward, please use `setQuestRewardCollected()`
+// If you want to mark the quest as not completed just to get the reward, please use `setQuestRewardCollected(,,0)`
 // instead.
 void setQuestCompleted(D2QuestData* d, unsigned int quest, unsigned int difficulty, int bool);
 
diff --git a/d2skills.h b/d2skills.h
index 15a91e0..7ecf888 100644
--- a/d2skills.h
+++ b/d2skills.h
@@ -5,6 +5,8 @@
 
 #include "d2strings.h"
 
+#define D2S_SKILL_NUMSKILLS 357
+
 const char* const skills[] = {
     D2S_SKILL_0,
     D2S_SKILL_1,
diff --git a/d2strings.h b/d2strings.h
index 05cb654..3949da8 100644
--- a/d2strings.h
+++ b/d2strings.h
@@ -1035,4 +1035,45 @@ const char* D2S_CHARPROGRESS_EXPANSION_TIER3_NAME_HARDCORE = "Guardian";
 #define D2S_QUEST_CHECKPOINT_430 NULL
 #define D2S_QUEST_CHECKPOINT_431 NULL
 
+// Waypoints
+#define D2S_WAYPOINT_0 "Rogue Encampment"
+#define D2S_WAYPOINT_1 "Cold Plains"
+#define D2S_WAYPOINT_2 "Stony Field"
+#define D2S_WAYPOINT_3 "Dark Wood"
+#define D2S_WAYPOINT_4 "Black Marsh"
+#define D2S_WAYPOINT_5 "Outer Cloister"
+#define D2S_WAYPOINT_6 "Jail Level 1"
+#define D2S_WAYPOINT_7 "Inner Cloister"
+#define D2S_WAYPOINT_8 "Catacombs Level 2"
+#define D2S_WAYPOINT_9 "Lut Gholein"
+#define D2S_WAYPOINT_10 "Sewers Level 2"
+#define D2S_WAYPOINT_11 "Dry Hills"
+#define D2S_WAYPOINT_12 "Halls of the Dead Level 2"
+#define D2S_WAYPOINT_13 "Far Oasis"
+#define D2S_WAYPOINT_14 "Lost City"
+#define D2S_WAYPOINT_15 "Palace Cellar Level 1"
+#define D2S_WAYPOINT_16 "Arcane Sanctuary"
+#define D2S_WAYPOINT_17 "Canyon of the Magi"
+#define D2S_WAYPOINT_18 "Kurast Docks"
+#define D2S_WAYPOINT_19 "Spider Forest"
+#define D2S_WAYPOINT_20 "Great Marsh"
+#define D2S_WAYPOINT_21 "Flayer Jungle"
+#define D2S_WAYPOINT_22 "Lower Kurast"
+#define D2S_WAYPOINT_23 "Kurast Bazaar"
+#define D2S_WAYPOINT_24 "Upper Kurast"
+#define D2S_WAYPOINT_25 "Travincal"
+#define D2S_WAYPOINT_26 "Durance of Hate Level 2"
+#define D2S_WAYPOINT_27 "Pandemonium Fortress"
+#define D2S_WAYPOINT_28 "City of the Damned"
+#define D2S_WAYPOINT_29 "River of Flames"
+#define D2S_WAYPOINT_30 "Harrogath"
+#define D2S_WAYPOINT_31 "Frigid Highlands"
+#define D2S_WAYPOINT_32 "Arreat Plateau"
+#define D2S_WAYPOINT_33 "Crystalline Passage"
+#define D2S_WAYPOINT_34 "Halls of Pain"
+#define D2S_WAYPOINT_35 "Glacial Trail"
+#define D2S_WAYPOINT_36 "Frozen Tundra"
+#define D2S_WAYPOINT_37 "The Ancient's Way"
+#define D2S_WAYPOINT_38 "Worldstone Keep Level 2"
+
 #endif
\ No newline at end of file